Inverse micellar compositions containing lubricant additives

ABSTRACT

This disclosure relates to lubricating engines using formulated lubricating oils to reduce wear and improve engine fuel efficiency. The formulated lubricating oils contain a major amount of a nonpolar lubricating oil base stock and a minor amount of one or more polar lubricating oil additives. The one or more polar lubricating oil additives include swollen inverse micelles dispersed in the nonpolar lubricating oil base stock. The swollen inverse micelles include (i) a liquid polar core containing a polar solvent and one or more polar lubricating oil additives having solubility in the polar solvent, and (ii) a layer of liquid surfactant molecules enclosing the liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core. A method of improving solubility of polar lubricating oil additives in a nonpolar lubricating oil base stock is also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patent application Ser. No. 13/625,281, filed Sep. 24, 2012, which is incorporated herein by reference in its entirety.

FIELD

This disclosure relates to lubricating engines using formulated lubricating oils to reduce wear and improve engine fuel efficiency. The formulated lubricating oils contain a major amount of a nonpolar lubricating oil base stock and a minor amount of one or more polar lubricating oil additives. The one or more polar lubricating oil additives comprise swollen inverse micelles dispersed in the nonpolar lubricating oil base stock. This disclosure also relates to a method of improving solubility of polar lubricating oil additives (e.g., inorganic friction and wear reducing additives) in a nonpolar lubricating oil base stock. This disclosure further relates to a method of improving surface performance of a lubricating oil in an engine lubricated with the lubricating oil.

BACKGROUND

Lubricants in commercial use today are prepared from a variety of natural and synthetic base stocks admixed with various additive packages and solvents depending upon their intended application. The base stocks typically include mineral oils, poly alpha olefins (PAO), gas-to-liquid base oils (GTL), silicone oils, phosphate esters, diesters, polyol esters, and the like.

A major trend for passenger car engine oils (PCEOs) is an overall improvement in quality as higher quality base stocks become more readily available. Typically the highest quality PCEO products are formulated with highly saturated base stocks such as PAOs or GTL stocks. These highly saturated stocks require the use of Group V base stocks such as ester to improve additive and deposit solubility.

Another major trend is the gradual reduction in the maximum allowable phosphorus contained in an engine oil to improve operational life. As the phosphorus content of engine oils is reduced, polar base stocks such as esters can accelerate wear and compromise vehicle durability.

Another major trend is the shift toward lower viscosity base stocks for improved fuel economy. This trend requires the use of use of high molecular weight polymers to provide protective films within lubricated contacts at high temperature. This approach has limitations in that these molecules increase the viscosity of the oil which has a negative impact on fuel economy and efficiency. These high molecular weight molecules are also sensitive to the harsh environment in the engine and typically degrade by oxidative chain scission and shear.

The current art is also limited in that conventional formulations tend to form acids which limit the life of the lubricant.

Therefore, there is a need for lubricating oils that provide appropriate solubility of lubricating oil additives and which also provide excellent surface performance, e.g., anti-wear and anti-corrosion performance. There is also a need to provide strong EHL films at contacts while using lower viscosity base stocks for improved fuel economy and efficiency.

SUMMARY

This disclosure relates to lubricating engines using formulated lubricating oils to reduce wear and improve engine fuel efficiency. The formulated lubricating oils contain a major amount of a nonpolar lubricating oil base stock and a minor amount of one or more polar lubricating oil additives. The one or more polar lubricating oil additives comprise swollen inverse micelles dispersed in the nonpolar lubricating oil base stock. The swollen inverse micelles comprise (i) a liquid polar core containing a polar solvent and one or more polar lubricating oil additives having solubility in the polar solvent, and (ii) a layer of liquid surfactant molecules enclosing the liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core. The inverse micelles are dispersed in the lubricating oil such that the lubricating oil exhibits improved anti-wear performance and improved engine fuel efficiency. The improved efficiency is enabled by the reduction of friction and improved elastohydrodynamic lubrication (EHL) film formation while using lower viscosity base stocks.

This disclosure also relates in part to a method of improving solubility of polar lubricating oil additives in a nonpolar lubricating oil base stock. The method comprises providing a lubricating oil comprising a nonpolar lubricating oil base stock as a major component and one or more polar lubricating oil additives as a minor component. The one or more polar lubricating oil additives comprise swollen inverse micelles dispersed in the nonpolar lubricating oil base stock. The swollen inverse micelles comprise (i) a liquid polar core containing a polar solvent and one or more polar lubricating oil additives having solubility in the polar solvent, and (ii) a layer of liquid surfactant molecules enclosing the liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.

In an embodiment, solubility of the polar lubricating oil additives in the nonpolar lubricating oil base stock is improved as compared to solubility achieved using a lubricating oil containing polar lubricating oil additives in a nonpolar lubricating oil base stock and not containing the swollen inverse micelles.

This disclosure yet further relates in part to a method of improving surface performance (e.g., anti-wear and anti-corrosion performance) of a lubricating oil in an engine lubricated with the lubricating oil. The method using as the lubricating oil a formulated oil comprising a nonpolar lubricating oil base stock as a major component and one or more polar lubricating oil additives as a minor component. The one or more polar lubricating oil additives comprise swollen inverse micelles dispersed in the nonpolar lubricating oil base stock. The swollen inverse micelles comprise (i) a liquid polar core containing a polar solvent and one or more polar lubricating oil additives having solubility in the polar solvent, and (ii) a layer of liquid surfactant molecules enclosing the liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.

In an embodiment, surface performance in an engine is improved as compared to surface performance in an engine using a lubricating oil containing polar lubricating oil additives in a nonpolar lubricating oil base stock and not containing the swollen inverse micelles.

This disclosure further relates in part to a swollen inverse micelle composition comprising (i) a liquid polar core containing a polar solvent and one or more polar lubricating oil additives having solubility in the polar solvent, and (ii) a layer of liquid surfactant molecules enclosing the liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.

This disclosure yet further relates in part to a process for making a swollen inverse micelle composition. The process comprises: providing one or more polar lubricating oil additives, a polar solvent, and a surfactant; and mixing the one or more polar lubricating oil additives, the polar solvent, and the surfactant under conditions sufficient to form the swollen inverse micelle composition. The swollen inverse micelle composition comprises (i) a liquid polar core containing the polar solvent and the one or more polar lubricating oil additives having solubility in the polar solvent, and (ii) a layer of liquid surfactant molecules enclosing the liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.

This disclosure also relates in part to a lubricating oil comprising a nonpolar lubricating oil base stock as a major component and a polar lubricating oil additive as a minor component. The polar lubricating oil additive comprises swollen inverse micelles dispersed in the nonpolar lubricating oil base stock. The swollen inverse micelles comprise (i) a liquid polar core containing a polar solvent and an antioxidant having solubility in the polar solvent, and (ii) a layer of liquid surfactant molecules enclosing the liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.

This disclosure further relates in part to a lubricating oil comprising a nonpolar lubricating oil base stock as a major component and a mixture of polar lubricating oil additives as a minor component. The mixture of polar lubricating oil additives comprises swollen inverse micelles dispersed in the nonpolar lubricating oil base stock. The mixture of swollen inverse micelles comprises: (a) a liquid polar core containing a polar solvent and an antioxidant having solubility in the polar solvent, and a layer of liquid surfactant molecules enclosing the liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core; and (b) a liquid polar core containing a polar solvent and a friction modifier having solubility in the polar solvent, and a layer of liquid surfactant molecules enclosing the liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.

This disclosure yet further relates in part to a lubricating oil comprising a nonpolar lubricating oil base stock as a major component and a mixture of polar lubricating oil additives as a minor component. The mixture of polar lubricating oil additives comprises (a) a first friction modifier comprising an organometallic molybdenum compound, and (b) a second friction modifier comprising swollen inverse micelles dispersed in the nonpolar lubricating oil base stock. The swollen inverse micelles comprise a liquid polar core containing a polar solvent and an inorganic molybdate compound having solubility in the polar solvent, and a layer of liquid surfactant molecules enclosing the liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core. Friction reduction and fuel efficiency are maintained or improved as compared to friction reduction and fuel efficiency achieved with a lubricating engine oil using singly the first friction modifier or the second friction modifier, as measured by one or more of ASTM D6079, SEQ VI-D and SEQ VI-E.

The advantages afforded by this disclosure include, for example, improved polar additive solubility in a nonpolar lubricating oil base stock, clarity and homogeneous finished lubricant phase, and enhanced surface performance through proper delivery of the performance additives. Enhanced performance is also achieved through improved EHL film formation.

It has been surprisingly found that solubility of polar lubricating oil additives (e.g., inorganic friction and wear reducing additives) in nonpolar lubricating oil base stocks is improved as compared to solubility achieved using a lubricating oil containing polar lubricating oil additives in a nonpolar lubricating oil base stock and not containing swollen inverse micelles. It has also been surprisingly found that surface performance in an engine is improved as compared to surface performance in an engine using a lubricating oil containing polar lubricating oil additives in a nonpolar lubricating oil base stock and not containing swollen inverse micelles.

It has further been surprisingly found that sustained antioxidant protection is afforded in a lubricating oil by utilizing one or more antioxidants in a swollen inverse micelle system. It has yet further been surprisingly found that extended low friction benefits are afforded from a friction modifier, as a lubricating oil ages, through the inverse micellization of both the friction modifier and one or more antioxidants. This inverse micellar system provides a protective barrier to isolate the antioxidant from competing chemical reactions with other additives. This inverse micellar system also provides protection from the harmful effects of oxidation on friction modifier performance.

It has been surprisingly found that an inorganic molybdate friction modifier contained in an inverse micelle system, and a mixture of the inorganic molybdate friction modifier in an inverse micelle system and an organometallic molybdate friction modifier not in an inverse micelle system, provides a significant friction benefit over a current premium synthetic motor oil formulation containing only a organometallic friction modifier as demonstrated through a lower frictional coefficient in a bench test. It has also been surprisingly found that the mixture of the inorganic molybdate friction modifier in the inverse micelle system and the organometallic molybdate friction modifier not in an inverse micelle system provides improved frictional performance over each of the individual friction modifiers contained in this system, demonstrating a synergistic effect. It has further been surprisingly found that the mixture of the inorganic molybdate friction modifier in the inverse micelle system and the organometallic molybdate friction modifier not in an inverse micelle system provides a benefit for fresh oil fuel economy relative to a current premium synthetic motor oil formulation as tested in industry standard engine tests.

Other objects and advantages of the present disclosure will become apparent from the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 graphically depicts the elastohydrodynamic lubrication (EHL) measurement of film thickness at 40° C. of the NB:25417-145-3 swollen inverse micelle system, Spectrasyn®-4, and premium synthetic 0W-20 motor oil, as set forth in Example 1.

FIG. 2 graphically depicts the elastohydrodynamic lubrication (EHL) measurement of film thickness at 60° C. of the NB:25417-145-3 swollen inverse micelle system, Spectrasyn®-4, and premium synthetic 0W-20 motor oil, as set forth in Example 1.

FIG. 3 graphically depicts the elastohydrodynamic lubrication (EHL) measurement of film thickness at 80° C. of the NB:25417-145-3 swollen inverse micelle system, Spectrasyn®-4, and premium synthetic 0W-20 motor oil, as set forth in Example 1.

FIG. 4 graphically depicts the elastohydrodynamic lubrication (EHL) measurement of film thickness at 100° C. of the NB:25417-145-3 swollen inverse micelle system, Spectrasyn®-4, and premium synthetic 0W-20 motor oil, as set forth in Example 1.

FIG. 5 graphically depicts friction versus temperature comparisons for ammonium tetrathiomolybdate including base stock control, surfactant control and tetraethylene glycol control (with swollen inverse micelles and without swollen inverse micelles).

FIG. 6 depicts a swollen inverse micelle system showing a polar solvent core with dissolved additive within a lubricant.

FIG. 7 graphically depicts the measurement of inverse micelle size using a Horiba laser light scattering particle size analyzer.

FIG. 8 is a 100× objective photograph of a macrocapsule (without polymer film) of polystyrene sulfonic acid (sodium salt) dissolved in tetraethylene glycol that is dispersed in oil without a surfactant.

FIG. 9 is a 100× objective photograph of an inverse micelle (with polymer film) of polystyrene sulfonic acid (sodium salt) dissolved in tetraethylene glycol that is dispersed in oil with a surfactant (i.e., PIBSA-PAM).

FIG. 10 shows the composition of formulations prepared in accordance with Example 4.

FIG. 11 graphically depicts results of DPA concentration indicated by the infrared absorbance of the aminic group as the lubricant is oxidized (i.e., Fourier Transform Infrared Spectroscopy (FTIR)) in accordance with Example 4.

FIG. 12 graphically depicts the same sample series as in FIG. 11 measured by FTIR for oxidation by infrared carbonyl absorbance as a function of time in the oxidation test in accordance with Example 4.

FIG. 13 shows the composition of formulations prepared in accordance with Example 5.

FIG. 14 shows the benefit of an inorganic molybdate friction modifier contained in an inverse micelle system (in blue) compared to a state of the art premium synthetic lubricant (in red) containing 0.15% of an organometallic friction modifier and not contained in an inverse micelle system, in lowering friction in a High Frequency Reciprocating Rig (HFRR) boundary lubricity test in accordance with Example 5.

FIG. 15 shows the benefit of the mixture of molybdenum additives in a formulation (i.e., an inorganic molybdate friction modifier contained in an inverse micelle system and an organometallic friction modifier not contained in an inverse micelle system), compared to a state of the art premium synthetic lubricant containing 0.15% (in red) and 0.3% (in purple) of an organometallic friction modifier not contained in an inverse micelle system in accordance with Example 5.

FIG. 16 shows the results of engine tests conducted on the mixture of molybdenum additives in a formulation (i.e., an inorganic molybdate friction modifier contained in an inverse micelle system and an organometallic friction modifier not contained in an inverse micelle system) compared to a premium GF-5 state of the art synthetic motor oil in accordance with Example 5.

FIG. 17 graphically shows that the inverse micelles are stable at high shear conditions and that under high shear conditions, the inverse micelles are self-healing and reform to smaller diameter spheres in accordance with Example 6.

FIG. 18 shows a microfluidizer in accordance with Example 6.

FIG. 19 graphically shows that microfluidizers afford higher shear rates than conventional mechanical mixers in accordance with Example 6.

FIG. 20 graphically shows that microfluidizers give a more uniform dispersion of particle size in accordance with Example 6.

FIG. 21 graphically shows an optimum inverse micelle diameter after high shear conditions in a microfluidizer (e.g., 0.082 μm mean diameter) in accordance with Example 6.

FIG. 22 graphically shows that reducing the inverse micelle diameter size from 0.2 μm to 0.1 μm shows benefit with regard to coefficient of friction in accordance with Example 6.

FIG. 23 graphically shows Dynamic Light Scattering (DLS) data for inverse micelle diameter size measurement during engine test in accordance with Example 6.

FIG. 24 graphically shows that inverse micelles are stable to ultrasonic shear in accordance with Example 6.

DETAILED DESCRIPTION

All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

This disclosure is a special inverse micelle technology for lubricants, which provides for the incorporation of sub-micron spheres of an insoluble polar solvent into a nonpolar base stock. This disclosure also provides a method of stabilizing the interface of the sphere with surfactants and optionally an outer polymer film. The invisible dispersed spheres provide the advantage of forming thick lubricating films while the surrounding base stock provides a relatively low overall viscosity to the oil. The polar solvent can also be used to dissolve polar additives which are not soluble in the base stock and/or incorporate higher concentrations of additives which have low solubility in the base stock.

This inverse micellar system can be used to efficiently transport polar molecules with a higher viscosity than the base stock to the contacts requiring elastohydrodynamic lubrication such as journal bearings. This system can be further used to solubilize, and carry in the base stock, surface active ingredients such as friction modifiers, anti-wear additives and antioxidants critical to all lubricated contacts. The surfactant protective coating of the dispersed swollen inverse micelles also efficiently provides self-healing properties (e.g., when swollen inverse micelles are sheared, the micelles spontaneously reform at a smaller size).

In accordance with this disclosure, there is provided a procedure of incorporating hydrocarbon insoluble compounds into lubricant formulations. It also provides a protective system of swollen inverse micelles to carry additives and efficiently deliver them in the high shear environment of the lubricated contact. These polar lubricating oil additives can be designed to impart better friction, anti-wear and antioxidant properties to the lubricant.

An additional benefit of this disclosure is the polar hydrocarbon carrier (i.e., polar solvent) in which the additive is dissolved. The viscosity of this carrier can be maximized to provide a shear triggered protective film at the lubricated contact. The inverse micellization of the high viscosity carrier provides the benefit of high film thickness within a relatively low viscosity lubricant. Furthermore, the polar hydrocarbon core can provide other benefits such as trapping and neutralizing acids formed during the oils use and providing a means to increase the thermal conductivity of the oil.

The lubricating engine oils of this disclosure can also be useful for applications irrespective of viscosity grade and/or base stock type. For example, the lubricating engine oils of this disclosure can be useful in automotive, marine, aviation, and industrial engine and machine components. The inverse micellar system of this disclosure can be used for a variety of applications, for example, isolating reactive additives, trapping water in lubricants, and the like. The lubricating oils of this disclosure can also be useful for lubricating machine components such as industrial paper machines, metal working tools, compressors, bearing greases, wind turbines, and the like.

In particular, this disclosure relates to inverse micelle compositions including a core containing one or more polar solvents and one or more lubricating oil additives in which the inverse micelles are dispersed in one or more lubricating base oils of mineral, synthetic or natural origin, and a liquid surfactant or liquid surfactant/polymer shell. This disclosure also relates to lubricating oils including the inverse micellar compositions. This disclosure further relates to the use of inverse micellar compositions as anti-wear, antioxidant and/or friction modifier additives for lubricant compositions.

As indicated above, the current art in formulating lubricants is limited by the oils solubility. It is an objective of this disclosure to solve this problem through the inverse micellization of polar solvents and polar lubricating oil additives in inverse micelles comprising a liquid surfactant protective layer. Inverse micellization is a process via which a product is enclosed in inverse micelles comprising a liquid surfactant or liquid surfactant/polymeric shell or membrane (typically polymeric) enclosing a liquid core containing the product. These inverse micelles have a diameter typically between 0.01 and 1000 μm. Depending on the particular molecules, applications are found in the areas of agriculture (fertilizers, pesticides), health (medications), cosmetics, textiles, and the like.

Lubricating Oil Base Stocks

A wide range of lubricating base oils is known in the art. Lubricating base oils that are useful in the present disclosure are both natural oils, and synthetic oils, and unconventional oils (or mixtures thereof) can be used unrefined, refined, or rerefined (the latter is also known as reclaimed or reprocessed oil). Unrefined oils are those obtained directly from a natural or synthetic source and used without added purification. These include shale oil obtained directly from retorting operations, petroleum oil obtained directly from primary distillation, and ester oil obtained directly from an esterification process. Refined oils are similar to the oils discussed for unrefined oils except refined oils are subjected to one or more purification steps to improve at least one lubricating oil property. One skilled in the art is familiar with many purification processes. These processes include solvent extraction, secondary distillation, acid extraction, base extraction, filtration, and percolation. Rerefined oils are obtained by processes analogous to refined oils but using an oil that has been previously used as a feed stock.

Groups I, II, III, IV and V are broad base oil stock categories developed and defined by the American Petroleum Institute (API Publication 1509; www.API.org) to create guidelines for lubricant base oils. Group I base stocks have a viscosity index of between 80 to 120 and contain greater than 0.03% sulfur and/or less than 90% saturates. Group II base stocks have a viscosity index of between 80 to 120, and contain less than or equal to 0.03% sulfur and greater than or equal to 90% saturates. Group III stocks have a viscosity index greater than 120 and contain less than or equal to 0.03% sulfur and greater than 90% saturates. Group IV includes polyalphaolefins (PAO). Group V base stock includes base stocks not included in Groups I-IV. The table below summarizes properties of each of these five groups.

Base Oil Properties Saturates Sulfur Viscosity Index Group I <90 and/or >0.03% and ≧80 and <120 Group II ≧90 and ≦0.03% and ≧80 and <120 Group III ≧90 and ≦0.03% and ≧120 Group IV Includes polyalphaolefms (PAO) and GTL products Group V All other base oil stocks not included in Groups I, II, III or IV

Natural oils include animal oils, vegetable oils (castor oil and lard oil, for example), and mineral oils. Animal and vegetable oils possessing favorable thermal oxidative stability can be used. Of the natural oils, mineral oils are preferred. Mineral oils vary widely as to their crude source, for example, as to whether they are paraffinic, naphthenic, or mixed paraffinic-naphthenic. Oils derived from coal or shale are also useful. Natural oils vary also as to the method used for their production and purification, for example, their distillation range and whether they are straight run or cracked, hydrorefined, or solvent extracted.

Group II and/or Group III hydroprocessed or hydrocracked base stocks, including synthetic oils such as polyalphaolefins, alkyl aromatics and synthetic esters are also well known base stock oils.

Synthetic oils include hydrocarbon oil. Hydrocarbon oils include oils such as polymerized and interpolymerized olefins (polybutylenes, polypropylenes, propylene isobutylene copolymers, ethylene-olefin copolymers, and ethylene-alphaolefin copolymers, for example). Polyalphaolefin (PAO) oil base stocks are commonly used synthetic hydrocarbon oil. By way of example, PAOs derived from C₈, C₁₀, C₁₂, C₁₄ olefins or mixtures thereof may be utilized. See U.S. Pat. Nos. 4,956,122; 4,827,064; and 4,827,073.

The number average molecular weights of the PAOs, which are known materials and generally available on a major commercial scale from suppliers such as ExxonMobil Chemical Company, Chevron Phillips Chemical Company, BP, and others, typically vary from 250 to 3,000, although PAO's may be made in viscosities up to 100 cSt (100° C.). The PAOs are typically comprised of relatively low molecular weight hydrogenated polymers or oligomers of alphaolefins which include, but are not limited to, C₂ to C₃₂ alphaolefins with the C₈ to C₁₆ alphaolefins, such as 1-octene, 1-decene, 1-dodecene and the like, being preferred. The preferred polyalphaolefins are poly-1-octene, poly-1-decene and poly-1-dodecene and mixtures thereof and mixed olefin-derived polyolefins. However, the dimers of higher olefins in the range of C₁₄ to C₁₈ may be used to provide low viscosity basestocks of acceptably low volatility. Depending on the viscosity grade and the starting oligomer, the PAOs may be predominantly trimers and tetramers of the starting olefins, with minor amounts of the higher oligomers, having a viscosity range of 1.5 to 12 cSt.

The PAO fluids may be conveniently made by the polymerization of an alphaolefin in the presence of a polymerization catalyst such as the Friedel-Crafts catalysts including, for example, aluminum trichloride, boron trifluoride or complexes of boron trifluoride with water, alcohols such as ethanol, propanol or butanol, carboxylic acids or esters such as ethyl acetate or ethyl propionate. For example, the methods disclosed by U.S. Pat. Nos. 4,149,178 or 3,382,291 may be conveniently used herein. Other descriptions of PAO synthesis are found in the following U.S. Pat. Nos. 3,742,082; 3,769,363; 3,876,720; 4,239,930; 4,367,352; 4,413,156; 4,434,408; 4,910,355; 4,956,122; and 5,068,487. The dimers of the C₁₄ to C₁₈ olefins are described in U.S. Pat. No. 4,218,330.

The hydrocarbyl aromatics can be used as base oil or base oil component and can be any hydrocarbyl molecule that contains at least 5% of its weight derived from an aromatic moiety such as a benzenoid moiety or naphthenoid moiety, or their derivatives. These hydrocarbyl aromatics include alkyl benzenes, alkyl naphthalenes, alkyl diphenyl oxides, alkyl naphthols, alkyl diphenyl sulfides, alkylated bisphenol A, alkylated thiodiphenol, and the like. The aromatic can be mono-alkylated, dialkylated, polyalkylated, and the like. The aromatic can be mono- or poly-functionalized. The hydrocarbyl groups can also be comprised of mixtures of alkyl groups, alkenyl groups, alkynyl, cycloalkyl groups, cycloalkenyl groups and other related hydrocarbyl groups. The hydrocarbyl groups can range from C₆ up to C₆₀ with a range of C₈ to C₂₀ often being preferred. A mixture of hydrocarbyl groups is often preferred, and up to three such substituents may be present. The hydrocarbyl group can optionally contain sulfur, oxygen, and/or nitrogen containing substituents. The aromatic group can also be derived from natural (petroleum) sources, provided at least 5% of the molecule is comprised of an above-type aromatic moiety. Viscosities at 100° C. of approximately 3 cSt to 50 cSt are preferred, with viscosities of approximately 3.4 cSt to 20 cSt often being more preferred for the hydrocarbyl aromatic component. In one embodiment, an alkyl naphthalene where the alkyl group is primarily comprised of 1-hexadecene is used. Other alkylates of aromatics can be advantageously used. Naphthalene or methyl naphthalene, for example, can be alkylated with olefins such as octene, decene, dodecene, tetradecene or higher, mixtures of similar olefins, and the like. Useful concentrations of hydrocarbyl aromatic in a lubricant oil composition can be 2% to 25%, preferably 4% to 20%, and more preferably 4% to 15%, depending on the application.

Esters comprise a useful base stock. Additive solvency and seal compatibility characteristics may be secured by the use of esters such as the esters of dibasic acids with monoalkanols and the polyol esters of monocarboxylic acids. Esters of the former type include, for example, the esters of dicarboxylic acids such as phthalic acid, succinic acid, alkyl succinic acid, alkenyl succinic acid, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acid, alkenyl malonic acid, etc., with a variety of alcohols such as butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, etc. Specific examples of these types of esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, etc.

Particularly useful synthetic esters are those which are obtained by reacting one or more polyhydric alcohols, preferably the hindered polyols (such as the neopentyl polyols, e.g., neopentyl glycol, trimethylol ethane, 2-methyl-2-propyl-1,3-propanediol, trimethylol propane, pentaerythritol and dipentaerythritol) with alkanoic acids containing at least 4 carbon atoms, preferably C₅ to C₃₀ acids such as saturated straight chain fatty acids including caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, and behenic acid, or the corresponding branched chain fatty acids or unsaturated fatty acids such as oleic acid, or mixtures of any of these materials.

Suitable synthetic ester components include the esters of trimethylol propane, trimethylol butane, trimethylol ethane, pentaerythritol and/or dipentaerythritol with one or more monocarboxylic acids containing from 5 to 10 carbon atoms. These esters are widely available commercially, for example, the Mobil P-41 and P-51 esters of ExxonMobil Chemical Company).

Other useful fluids of lubricating viscosity include non-conventional or unconventional base stocks that have been processed, preferably catalytically, or synthesized to provide high performance lubrication characteristics.

Non-conventional or unconventional base stocks/base oils include one or more of a mixture of base stock(s) derived from one or more Gas-to-Liquids (GTL) materials, as well as isomerate/isodewaxate base stock(s) derived from natural wax or waxy feeds, mineral and or non-mineral oil waxy feed stocks such as slack waxes, natural waxes, and waxy stocks such as gas oils, waxy fuels hydrocracker bottoms, waxy raffinate, hydrocrackate, thermal crackates, or other mineral, mineral oil, or even non-petroleum oil derived waxy materials such as waxy materials received from coal liquefaction or shale oil, and mixtures of such base stocks.

GTL materials are materials that are derived via one or more synthesis, combination, transformation, rearrangement, and/or degradation/deconstructive processes from gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks such as hydrogen, carbon dioxide, carbon monoxide, water, methane, ethane, ethylene, acetylene, propane, propylene, propyne, butane, butylenes, and butynes. GTL base stocks and/or base oils are GTL materials of lubricating viscosity that are generally derived from hydrocarbons; for example, waxy synthesized hydrocarbons, that are themselves derived from simpler gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks. GTL base stock(s) and/or base oil(s) include oils boiling in the lube oil boiling range (1) separated/fractionated from synthesized GTL materials such as, for example, by distillation and subsequently subjected to a final wax processing step which involves either or both of a catalytic dewaxing process, or a solvent dewaxing process, to produce lube oils of reduced/low pour point; (2) synthesized wax isomerates, comprising, for example, hydrodewaxed or hydroisomerized cat and/or solvent dewaxed synthesized wax or waxy hydrocarbons; (3) hydrodewaxed or hydroisomerized cat and/or solvent dewaxed Fischer-Tropsch (F-T) material (i.e., hydrocarbons, waxy hydrocarbons, waxes and possible analogous oxygenates); preferably hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxing dewaxed F-T waxy hydrocarbons, or hydrodewaxed or hydroisomerized/followed by cat (or solvent) dewaxing dewaxed, F-T waxes, or mixtures thereof.

GTL base stock(s) and/or base oil(s) derived from GTL materials, especially, hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxed wax or waxy feed, preferably F-T material derived base stock(s) and/or base oil(s), are characterized typically as having kinematic viscosities at 100° C. of from 2 mm²/s to 50 mm²/s (ASTM D445). They are further characterized typically as having pour points of −5° C. to −40° C. or lower (ASTM D97). They are also characterized typically as having viscosity indices of 80 to 140 or greater (ASTM D2270).

In addition, the GTL base stock(s) and/or base oil(s) are typically highly paraffinic (>90% saturates), and may contain mixtures of monocycloparaffins and multicycloparaffins in combination with non-cyclic isoparaffins. The ratio of the naphthenic (i.e., cycloparaffin) content in such combinations varies with the catalyst and temperature used. Further, GTL base stock(s) and/or base oil(s) typically have very low sulfur and nitrogen content, generally containing less than 10 ppm, and more typically less than 5 ppm of each of these elements. The sulfur and nitrogen content of GTL base stock(s) and/or base oil(s) obtained from F-T material, especially F-T wax, is essentially nil. In addition, the absence of phosphorous and aromatics make this materially especially suitable for the formulation of low SAP products.

The term GTL base stock and/or base oil and/or wax isomerate base stock and/or base oil is to be understood as embracing individual fractions of such materials of wide viscosity range as recovered in the production process, mixtures of two or more of such fractions, as well as mixtures of one or two or more low viscosity fractions with one, two or more higher viscosity fractions to produce a blend wherein the blend exhibits a target kinematic viscosity.

The GTL material, from which the GTL base stock(s) and/or base oil(s) is/are derived is preferably an F-T material (i.e., hydrocarbons, waxy hydrocarbons, wax).

In addition, the GTL base stock(s) and/or base oil(s) are typically highly paraffinic (>90% saturates), and may contain mixtures of monocycloparaffins and multicycloparaffins in combination with non-cyclic isoparaffins. The ratio of the naphthenic (i.e., cycloparaffin) content in such combinations varies with the catalyst and temperature used. Further, GTL base stock(s) and/or base oil(s) and hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed base stock(s) and/or base oil(s) typically have very low sulfur and nitrogen content, generally containing less than 10 ppm, and more typically less than 5 ppm of each of these elements. The sulfur and nitrogen content of GTL base stock(s) and/or base oil(s) obtained from F-T material, especially F-T wax, is essentially nil. In addition, the absence of phosphorous and aromatics make this material especially suitable for the formulation of low sulfur, sulfated ash, and phosphorus (low SAP) products.

Base oils for use in the formulated lubricating oils useful in the present disclosure are any of the variety of oils corresponding to API Group I, Group II, Group III, Group IV, and Group V oils and mixtures thereof, preferably API Group II, Group III, Group IV, and Group V oils and mixtures thereof, more preferably the Group III to Group V base oils due to their exceptional volatility, stability, viscometric and cleanliness features. Minor quantities of Group I stock, such as the amount used to dilute additives for blending into formulated lube oil products, can be tolerated but should be kept to a minimum, i.e. amounts only associated with their use as diluents/carrier oil for additives used on an “as-received” basis. Even in regard to the Group II stocks, it is preferred that the Group II stock be in the higher quality range associated with that stock, i.e. a Group II stock having a viscosity index in the range 100<VI<120.

The base oil constitutes the major component of the engine oil lubricant composition of the present disclosure and typically is present in an amount ranging from 50 to 99 weight percent, preferably from 70 to 95 weight percent, and more preferably from 85 to 95 weight percent, based on the total weight of the composition. The base oil may be selected from any of the synthetic or natural oils typically used as crankcase lubricating oils for spark-ignited and compression-ignited engines. The base oil conveniently has a kinematic viscosity, according to ASTM standards, of 2.5 cSt to 12 cSt (or mm²/s) at 100° C. and preferably of 2.5 cSt to 9 cSt (or mm²/s) at 100° C. Mixtures of synthetic and natural base oils may be used if desired.

Polar Solvents

Illustrative polar solvents useful in the swollen inverse micelles include, for example, glycols, alcohols, esters, ethers, carboxylic acids, amines, and other organic compounds containing one or more polar functional groups (e.g., phosphate, sulfonate, sulfate, silicone). In particular, useful polar solvents include monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, triethylene glycol monomethyl ether, triethylene glocol dimethyl ether, tripropylene glycol, tripropylene glycol butyl ether (also known as Dowanol™ TPnB), tripropylene glycol methyl ether (also known as Dowanol™ TPM), diethylene glycol dimethyl ether (also known as diglyme), and the like.

The polar solvent can be present in an amount from 0.1 weight percent to 20 weight percent, preferably from 1 weight percent to 10 weight percent, and more preferably from 2 weight percent to 5 weight percent, based on the total weight of the lubricating oil. The polar solvent is present in the lubricating oil in an amount sufficient to impart solubility to the polar lubricating oil additives, and to form the swollen inverse micelles.

Surfactants

Suitable surfactants useful in this disclosure typically contain a polar group attached to a relatively high molecular weight hydrocarbon chain. The polar group typically contains at least one element of nitrogen, oxygen, or phosphorus. Typical hydrocarbon chains contain 50 to 400 carbon atoms.

Chemically, many surfactants may be characterized as phenates, sulfonates, sulfurized phenates, salicylates, naphthenates, stearates, carbamates, thiocarbamates, phosphorus derivatives. A particularly useful class of surfactants are the alkenylsuccinic derivatives, typically produced by the reaction of a long chain hydrocarbyl substituted succinic compound, usually a hydrocarbyl substituted succinic anhydride, with a polyhydroxy or polyamino compound. The long chain hydrocarbyl group constituting the oleophilic portion of the molecule which confers solubility in the oil, is normally a polyisobutylene group. Many examples of this type of surfactant are well known commercially and in the literature. Exemplary U.S. patents describing such surfactants are U.S. Pat. Nos. 3,172,892; 3,215,707; 3,219,666; 3,316,177; 3,341,542; 3,444,170; 3,454,607; 3,541,012; 3,630,904; 3,632,511; 3,787,374 and 4,234,435. Other types of surfactant are described in U.S. Pat. Nos. 3,036,003; 3,200,107; 3,254,025; 3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,413,347; 3,697,574; 3,725,277; 3,725,480; 3,726,882; 4,454,059; 3,329,658; 3,449,250; 3,519,565; 3,666,730; 3,687,849; 3,702,300; 4,100,082; 5,705,458. A further description of surfactants may be found, for example, in European Patent Application No. 471 071, to which reference is made for this purpose.

Hydrocarbyl-substituted succinic acid and hydrocarbyl-substituted succinic anhydride derivatives are useful surfactants. In particular, succinimide, succinate esters, or succinate ester amides prepared by the reaction of a hydrocarbon-substituted succinic acid compound preferably having at least 50 carbon atoms in the hydrocarbon substituent, with at least one equivalent of an alkylene amine are particularly useful.

Succinimides are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and amines. Molar ratios can vary depending on the polyamine. For example, the molar ratio of hydrocarbyl substituted succinic anhydride to TEPA can vary from 1:1 to 5:1. Representative examples are shown in U.S. Pat. Nos. 3,087,936; 3,172,892; 3,219,666; 3,272,746; 3,322,670; and 3,652,616, 3,948,800; and Canada Patent No. 1,094,044.

Succinate esters are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and alcohols or polyols. Molar ratios can vary depending on the alcohol or polyol used. For example, the condensation product of a hydrocarbyl substituted succinic anhydride and pentaerythritol is a useful surfactant.

Succinate ester amides are formed by condensation reaction between hydrocarbyl substituted succinic anhydrides and alkanol amines. For example, suitable alkanol amines include ethoxylated polyalkylpolyamines, propoxylated polyalkylpolyamines and polyalkenylpolyamines such as polyethylene polyamines. One example is propoxylated hexamethylenediamine. Representative examples are shown in U.S. Pat. No. 4,426,305.

The molecular weight of the hydrocarbyl substituted succinic anhydrides used in the preceding paragraphs will typically range between 800 and 2,500. The above products can be post-reacted with various reagents such as sulfur, oxygen, formaldehyde, carboxylic acids such as oleic acid. The above products can also be post reacted with boron compounds such as boric acid, borate esters or highly borated surfactants, to form borated surfactants generally having from 0.1 to 5 moles of boron per mole of surfactant reaction product.

Mannich base surfactants are made from the reaction of alkylphenols, formaldehyde, and amines. See U.S. Pat. No. 4,767,551, which is incorporated herein by reference. Process aids and catalysts, such as oleic acid and sulfonic acids, can also be part of the reaction mixture. Molecular weights of the alkylphenols range from 800 to 2,500. Representative examples are shown in U.S. Pat. Nos. 3,697,574; 3,703,536; 3,704,308; 3,751,365; 3,756,953; 3,798,165; and 3,803,039.

Typical high molecular weight aliphatic acid modified Mannich condensation products useful in this disclosure can be prepared from high molecular weight alkyl-substituted hydroxyaromatics or HN®₂ group-containing reactants.

Hydrocarbyl substituted amine surfactant additives are well known to one skilled in the art; see, for example, U.S. Pat. Nos. 3,275,554; 3,438,757; 3,565,804; 3,755,433, 3,822,209, and 5,084,197.

Other useful surfactants include, for example, carboxylic acids (e.g., oleic acid), alkyl amines (e.g., oleylamine), reaction products of carboxylic acids and alkyl amines (e.g., dialkyl amides), and the like.

Preferred surfactants include borated and non-borated succinimides, including those derivatives from mono-succinimides, bis-succinimides, and/or mixtures of mono- and bis-succinimides, wherein the hydrocarbyl succinimide is derived from a hydrocarbylene group such as polyisobutylene having a Mn of from 500 to 5000 or a mixture of such hydrocarbylene groups. Other preferred surfactants include succinic acid-esters and amides, alkylphenol-polyamine-coupled Mannich adducts, their capped derivatives, and other related components. A preferred surfactant is polyisobutylene succinimide polyamine (PIBSA-PAM). Such additives may be used in an amount of 0.1 to 20 weight percent, preferably 0.5 to 8 weight percent.

The surfactant can be present in an amount from 0.1 weight percent to 10 weight percent, preferably from 0.2 weight percent to 5 weight percent, and more preferably from 0.5 weight percent to 2 weight percent, based on the total weight of the lubricating oil. The surfactant is present in the lubricating oil in an amount sufficient to form a layer of liquid surfactant molecules enclosing the liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core, and to form the swollen inverse micelles.

Polar Lubricating Oil Additives

Illustrative polar lubricating oil additives useful in the swollen inverse micelles include, for example, dispersants, detergents, corrosion inhibitors, rust inhibitors, metal deactivators, antioxidants, anti-wear agents and/or extreme pressure additives, anti-seizure agents, wax modifiers, viscosity index improvers, viscosity modifiers, fluid-loss additives, seal compatibility agents, friction modifiers, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, antifoam agents, and pour point depressants. Illustrative polar lubricating oil additives useful in the swollen inverse micelles include, for example, inorganic lubricating oil additives.

In particular, illustrative polar lubricating oil additives include friction modifiers such as ammonium tetrathiomolybdate, ammonium molybdate, sodium molybdate, sodium molybdenum dehydrate, molybdenum disulfide, molybdenum carbide, molybdenum (VI) oxide, molybdenum di-n-butyl dithiocarbamate, (propylcyclopentadienyl molybdenum tricarbonyl dimer, and the like; also organic and inorganic borated compounds and the like; antioxidants such as butylated hydroxytoluene (BHT), 2,6-di-tert-butyl phenol, 2,6-di-tert-butyl cresol, alkylated diphenylamines, and the like; and anti-wear agents such as zinc dialkyldithiophosphate (ZDDP), tricresyl phosphate, sulfurized olefins, elemental sulfur and compounds which produce sulfur in situ such as ammonium or sodium thiosulfate dissolved in the polar core, and the like.

In general, the polar lubricating oil additives can be present in an amount from 0.05 weight percent to 5 weight percent, preferably from 0.1 weight percent to 2 weight percent, and more preferably from 0.2 weight percent to 1 weight percent, based on the total weight of the lubricating oil. The polar lubricating oil additives are present in the lubricating oil in an amount sufficient to form the polar core and to form the swollen inverse micelles.

Swollen Inverse Micelles

This disclosure includes a swollen inverse micelle system comprised of a liquid polar solvent core surrounded by a self-assembled layer of liquid surfactant molecules, with a polar head oriented towards the polar solvent core. The liquid polar solvent core may contain one or more polar lubricant additives, including friction modifiers, antioxidants, and corrosion inhibitors, and rust inhibitors. The system provides a method to incorporate oil-insoluble polar lubricant performance additives into a lubricant formulation.

The additives contained in the swollen inverse micelle system are stable in a fully formulated lubricant and will not precipitate or separate over time under normal storage conditions. In application at elevated temperatures, pressures or shear stress, the additives will be slowly released into the oil, through one or more of the following mechanisms: 1) diffusion, 2) thermal/oxidative degradation of the liquid surfactant layer, 3) deformation of the micelle system through high pressures or shear stress.

The micelle system also provides an added level of thermal and oxidative protection to the contained lubricant additives from the external environment, allowing the additives to degrade at a much slower rate, resulting in extended additive performance. This additive protection can be further enhanced by incorporating a lubricant performance additive along with a polar antioxidant additive within the polar solvent core of the micelle system, to deliver oxidative protection from within the micelle system itself.

The swollen reverse micelle can also be used as a miniature reactor, as it is partially isolated from the bulk environment of the lubricant. The temperatures and pressures inside the micelles could allow for reactions to occur locally, in the internal polar solvent phase. For example, the molybdate friction modifier may be converted to a better friction modifier (MoS₂, Mo oxides, etc.) within the micelle than if it was in a bulk phase. Acid base reactions within the micelle could also result in the formation of anti-wear agents such sodium thiosulfate, which is soluble in glycol, and can form colloidal sulfur within the micelle if it sees acid.

A particular set of conditions are needed to form the inverse or reverse micelle systems of this disclosure.

First, a critical surfactant concentration as indicated by the critical micelle concentration (CMC) and Dynamic Light Scattering (DLS) data is needed. Typical critical surfactant concentrations can range from about 0.05 wt. % to about 2 wt. %, or from about 0.1 wt. % to about 1.75 wt. %, or from about 0.5 wt. % to about 1.5 wt. %.

Second, a very low interfacial tension is needed. Interfacial tension will be affected by the additives incorporated into the polar solvent core. Without the additives, the micelle has a larger mean diameter and is not optically clear (i.e., there is a haze). However with the molybdate additive, the interfacial tension is significantly reduced, decreasing the mean diameter and allowing the solution to be optically clear. Typical interfacial tension can range from about 0.1 mN/m to about 60 mN/m, or from about 0.5 mN/m to about 30 mN/m, or from about 1 mN/m to about 10 mN/m.

Third, sufficient shear during the manufacturing process of the swollen inverse micelle system is needed to achieve sub-micron size. A microfluidizer is a preferred device that can achieve the desired micelle size (e.g., from about 0.05 to about 0.5 micron mean diameter). Typical shear can range from about 1,000 sec.-1 to about 50,000,000 sec.-1, or from about 20,000 sec.-1 to about 20,000,000, or from about 500,000 sec.-1 to about 10,000,000 sec.-1.

The term “swollen inverse micelles” means inverse micelles comprising a liquid core containing a polar solvent and one or more polar lubricating oil additives having solubility in the polar solvent, and a liquid surfactant or liquid surfactant/polymeric layer (typically polymeric) enclosing the liquid core. When the swollen inverse micelles are sheared, they spontaneously reform at a smaller size (i.e., they are self-healing). The swollen inverse micelles protect the polar lubricating oil additives from negative interactions by isolating them within the liquid core. Additional protection against oxidation is provided by incorporating an antioxidant(s) along with one or more other additives into swollen inverse micelles to extend the useful life of the additives. The solubility of polar additives is improved by dissolving the polar additives in a polar solvent which forms the core of the micelle.

The swollen inverse micelles of this disclosure are approximately of spherical shape. When speaking in terms of diameter, or size of the swollen inverse micelles, reference is made to their largest dimension. The diameter of the swollen inverse micelles according to this disclosure is preferably between 0.01 and 50 μm, more preferably between 0.01 and 10 μm, or between 0.01 and 1.5 μm, or between 0.01 and 1 μm, or between 0.01 and 0.75 μm, or between 0.05 and 0.5 μm. It is desirable that the swollen inverse micelles should be of homogeneous size. It is also desirable that the preferably homogeneous size is of the order of a few hundred nanometers, typically less than 1 micron, for example less than 0.75 microns, in particular less than 0.5 microns, so as to provide optical clarity to the lubricating oil.

The dispersion of swollen inverse micelles in a liquid lubricant oil is complex and requires stabilizing the core with a surfactant and achieving sub-micron size (diameter) of the swollen inverse micelles. A very low interfacial tension, as a result of the inorganic friction modifier dissolved in the polar core, is an important factor for achieving sub-micron size. Very high shear rates on the order of 10⁷ sec⁻¹ are applied to achieve a desired average particle size (e.g., about 0.05 to about 0.5 μm).

The swollen inverse micelles of this disclosure can have a liquid surfactant or liquid surfactant/polymeric shell or membrane enclosing the core. The liquid surfactant or liquid surfactant/polymeric protective shell can insulate the polar solvent and polar lubricating oil additives from the outside environment, providing protection to the polar lubricating oil additives from negative interactions by isolating them within the liquid core, protection against oxidation by incorporating an antioxidant(s) along with one or more other additives in the inverse micelle system to extend the useful life of the additives, and improving of polar additives by dissolving the polar additives in a polar solvent which forms the core of the micelle.

The swollen inverse micelles of this disclosure have a core that is surrounded by a liquid surfactant or liquid surfactant/polymeric shell or membrane that is stable to moderate shear and high temperatures. When swollen inverse micelles are sheared, the micelles spontaneously reform at a smaller size (i.e., they are self-healing). At high shear rates, the swollen inverse micelles elongate and form a protective film between the moving contact (e.g., bearing, piston rings, etc.) as shown in FIGS. 1-4. Also, as shown in FIGS. 1-4, a protective film is provided that is stable at high temperatures. Further, as shown in FIGS. 1-4, the film is maintained as the temperature increases while the premium conventional lubricant shows film degradation as temperature increases.

The constituent polymers of the liquid surfactant/polymeric shell of the swollen inverse micelles according to this disclosure can have good heat resistance (i.e., do not degrade at extreme temperatures which may be encountered when in service, i.e., of the order of 150° C. to 160° C.), and good mechanical strength so that they can withstand the high shear levels encountered in engines. The liquid surfactant/polymeric shell of the swollen inverse micelles according to this disclosure may be formed for example of polymers of polystyrene sulfonic acid (or salt), polyester, polyamide, polyurethane, polyurea type, or the copolymers thereof, optionally with other monomers, polyacrylonitriles, vinyl resins or aminoplast resins. Polyureas, known for their good properties, are particularly preferred. They also have good mechanical resistance and good heat resistance.

The swollen inverse micelles of this disclosure can be prepared by conventional methods known in the art. For example, a polar lubricating oil additive can be mixed with a polar solvent and the resulting product can be added to a lubricating oil base stock. The resulting product can be mixed under low and/or high shear conditions for a time (e.g., from 5 minutes to 2 hours) and at a temperature (e.g., from 15° C. to 80° C.) sufficient to form a homogeneous lubricant containing swollen inverse micelles.

The liquid surfactant/polymeric shell or membrane (typically polymeric) enclosing the solid or liquid core can be prepared by conventional methods known in the art. For example, an oil soluble cross-linking agent can be added to the oil continuous phase after the polar phase is dispersed. Alternatively, the functional groups on additive(s) in the oil continuous phase (such as the polyamine groups on typical surfactants) can be used to react with polymer(s) in the polar core and form a polymer film at the interface.

Polar lubricant additives contained in the swollen inverse micelle system are an alternative method to hard-sphere polymer microencapsulated additives or polymer matrix microencapsulated additives, which may also provide slow release and enhanced thermal and oxidative protection to lubricant additives. However, the inverse micelle systems provide several advantages over the microencapsulated systems.

At high pressure or shear stress, all of these systems (i.e., swollen inverse micelle, hard-sphere polymer microcapsules, and polymer matrix microcapsules) will rupture or divide releasing some additive into the oil. However, unlike the microcapsules, the inverse micelle system is self-healing and the surfactant molecules reform their liquid layer around the polar additive-solvent solution.

When the formulation is comprised of a surfactant level above the CMC for that surfactant, free surfactant molecules will exist in the lubricant, which allows for replacement or exchange of surfactant molecules in the liquid surfactant layer of the micelle system as these molecules begin to thermally or oxidatively degrade. This aids the extension of the micelle system.

The surfactant molecules not only serve to deliver and protect polar additives to a lubricant, but they can also serve to disperse high molecular weight oxidation products which reduces engine oil deposit formation and improves the cleanliness performance of the lubricant. Thus, the inverse micelle system is able to provide performance to the lubricant even after the comprised additive is released. On the other hand, the high molecular weight microcapsule polymeric materials left behind after the additive release have not been shown to provide any additional performance benefits and may promote the formation of deposits or reduce oil flow by clogging the oil filter.

The surfactant shell is a permeable membrane that can potentially act as a hydrogen ion trap that neutralizes acid, traps water and other bad byproducts of oxidation and aging.

The swollen inverse micelles are present in the lubricating oil in an amount sufficient to impart to the lubricating oil improved friction reduction and improved engine fuel efficiency. In particular, the swollen inverse micelles can be present in an amount from 0.1 weight percent to 10 weight percent or greater, preferably from 0.25 weight percent to 9.5 weight percent, and more preferably from 0.5 weight percent to 9 weight percent, based on the total weight of the lubricating oil.

Other Additives

The formulated lubricating oil useful in the present disclosure may additionally contain one or more of the other commonly used lubricating oil performance additives including but not limited to dispersants, detergents, corrosion inhibitors, rust inhibitors, metal deactivators, other anti-wear agents and/or extreme pressure additives, anti-seizure agents, wax modifiers, viscosity index improvers, viscosity modifiers, fluid-loss additives, seal compatibility agents, friction modifiers, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, and others. For a review of many commonly used additives, see Klamann in Lubricants and Related Products, Verlag Chemie, Deerfield Beach, Fla.; ISBN 0-89573-177-0. Reference is also made to “Lubricant Additives” by M. W. Ranney, published by Noyes Data Corporation of Parkridge, N.J. (1973).

The types and quantities of performance additives used in combination with the instant disclosure in lubricant compositions are not limited by the examples shown herein as illustrations.

Friction Modifiers

A friction modifier is any material or materials that can alter the coefficient of friction of a surface lubricated by any lubricant or fluid containing such material(s). Friction modifiers, also known as friction reducers, or lubricity agents or oiliness agents, and other such agents that change the ability of base oils, formulated lubricant compositions, or functional fluids, to modify the coefficient of friction of a lubricated surface may be effectively used in combination with the base oils or lubricant compositions of the present disclosure if desired. Friction modifiers that lower the coefficient of friction are particularly advantageous in combination with the base oils and lube compositions of this disclosure. Friction modifiers may include metal-containing compounds or materials as well as ashless compounds or materials, or mixtures thereof. Metal-containing friction modifiers may include metal salts or metal ligand complexes where the metals may include alkali, alkaline earth, or transition group metals. Such metal-containing friction modifiers may also have low-ash characteristics. Transition metals may include Mo, Sb, Sn, Fe, Cu, Zn, and others. Ligands may include hydrocarbyl derivative of alcohols, polyols, glycerols, partial ester glycerols, thiols, carboxylates, carbamates, thiocarbamates, dithiocarbamates, phosphates, thiophosphates, dithiophosphates, amides, imides, amines, thiazoles, thiadiazoles, dithiazoles, diazoles, triazoles, and other polar molecular functional groups containing effective amounts of O, N, S, or P, individually or in combination. In particular, Mo-containing compounds can be particularly effective such as for example Mo-dithiocarbamates, Mo(DTC), Mo-dithiophosphates, Mo(DTP), Mo-amines, Mo (Am), Mo-alcoholates, Mo-alcohol-amides, etc. See U.S. Pat. Nos. 5,824,627, 6,232,276, 6,153,564, 6,143,701, 6,110,878, 5,837,657, 6,010,987, 5,906,968, 6,734,150, 6,730,638, 6,689,725, 6,569,820; WO 99/66013; WO 99/47629; and WO 98/26030.

Ashless friction modifiers may also include lubricant materials that contain effective amounts of polar groups, for example, hydroxyl-containing hydrocarbyl base oils, glycerides, partial glycerides, glyceride derivatives, and the like. Polar groups in friction modifiers may include hydrocarbyl groups containing effective amounts of O, N, S, or P, individually or in combination. Other friction modifiers that may be particularly effective include, for example, salts (both ash-containing and ashless derivatives) of fatty acids, fatty alcohols, fatty amides, fatty esters, hydroxyl-containing carboxylates, and comparable synthetic long-chain hydrocarbyl acids, alcohols, amides, esters, hydroxy carboxylates, and the like. In some instances fatty organic acids, fatty amines, and sulfurized fatty acids may be used as suitable friction modifiers.

Useful concentrations of friction modifiers may range from 0.01 weight percent to 10-15 weight percent or more, often with a preferred range of 0.1 weight percent to 5 weight percent. Concentrations of molybdenum-containing materials are often described in terms of Mo metal concentration. Advantageous concentrations of Mo may range from 10 ppm to 3000 ppm or more, and often with a preferred range of 20-2000 ppm, and in some instances a more preferred range of 30-1000 ppm. Friction modifiers of all types may be used alone or in mixtures with the materials of this disclosure. Often mixtures of two or more friction modifiers, or mixtures of friction modifier(s) with alternate surface active material(s), are also desirable.

Antioxidants

Antioxidants retard the oxidative degradation of base oils during service. Such degradation may result in deposits on metal surfaces, the presence of sludge, or a viscosity increase in the lubricant. One skilled in the art knows a wide variety of oxidation inhibitors that are useful in lubricating oil compositions. See, Klamann in Lubricants and Related Products, op cite, and U.S. Pat. Nos. 4,798,684 and 5,084,197, for example.

Useful antioxidants include hindered phenols. These phenolic antioxidants may be ashless (metal-free) phenolic compounds or neutral or basic metal salts of certain phenolic compounds. Typical phenolic antioxidant compounds are the hindered phenolics which are the ones which contain a sterically hindered hydroxyl group, and these include those derivatives of dihydroxy aryl compounds in which the hydroxyl groups are in the o- or p-position to each other. Typical phenolic antioxidants include the hindered phenols substituted with C₆+ alkyl groups and the alkylene coupled derivatives of these hindered phenols. Examples of phenolic materials of this type 2-t-butyl-4-heptyl phenol; 2-t-butyl-4-octyl phenol; 2-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4-heptyl phenol; 2,6-di-t-butyl-4-dodecyl phenol; 2-methyl-6-t-butyl-4-heptyl phenol; and 2-methyl-6-t-butyl-4-dodecyl phenol. Other useful hindered mono-phenolic antioxidants may include for example hindered 2,6-di-alkyl-phenolic proprionic ester derivatives. Bis-phenolic antioxidants may also be advantageously used in combination with the instant disclosure. Examples of ortho-coupled phenols include: 2,2′-bis(4-heptyl-6-T-butyl-phenol); 2,2′-bis(4-octyl-6-t-butyl-phenol); and 2,2′-bis(4-dodecyl-6-t-butyl-phenol). Para-coupled bisphenols include for example 4,4′-bis(2,6-di-t-butyl phenol) and 4,4′-methylene-bis(2,6-di-t-butyl phenol).

Non-phenolic oxidation inhibitors which may be used include aromatic amine antioxidants and these may be used either as such or in combination with phenolics. Typical examples of non-phenolic antioxidants include: alkylated and non-alkylated aromatic amines such as aromatic monoamines of the formula R⁸R⁹R¹⁰N where R⁸ is an aliphatic, aromatic or substituted aromatic group, R⁹ is an aromatic or a substituted aromatic group, and R¹⁰ is H, alkyl, aryl or R¹¹S(O)_(X)R¹² where R¹¹ is an alkylene, alkenylene, or aralkylene group, R¹² is a higher alkyl group, or an alkenyl, aryl, or alkaryl group, and x is 0, 1 or 2. The aliphatic group R⁸ may contain from 1 to 20 carbon atoms, and preferably contains from 6 to 12 carbon atoms. The aliphatic group is a saturated aliphatic group. Preferably, both R⁸ and R⁹ are aromatic or substituted aromatic groups, and the aromatic group may be a fused ring aromatic group such as naphthyl. Aromatic groups R⁸ and R⁹ may be joined together with other groups such as S.

Typical aromatic amines antioxidants have alkyl substituent groups of at least 6 carbon atoms. Examples of aliphatic groups include hexyl, heptyl, octyl, nonyl, and decyl. Generally, the aliphatic groups will not contain more than 14 carbon atoms. The general types of amine antioxidants useful in the present compositions include diphenylamines, phenyl naphthylamines, phenothiazines, imidodibenzyls and diphenyl phenylene diamines. Mixtures of two or more aromatic amines are also useful. Polymeric amine antioxidants can also be used. Particular examples of aromatic amine antioxidants useful in the present disclosure include: p,p′-dioctyldiphenylamine; t-octylphenyl-alpha-naphthylamine; phenyl-alphanaphthylamine; and p-octylphenyl-alpha-naphthylamine.

Sulfurized alkyl phenols and alkali or alkaline earth metal salts thereof also are useful antioxidants.

Preferred antioxidants include hindered phenols, arylamines. These antioxidants may be used individually by type or in combination with one another. Such additives may be used in an amount of 0.01 to 5 weight percent, preferably 0.01 to 1.5 weight percent, more preferably zero to less than 1.5 weight percent, most preferably zero.

Dispersants

During engine operation, oil-insoluble oxidation byproducts are produced. Dispersants help keep these byproducts in solution, thus diminishing their deposition on metal surfaces. Dispersants used in the formulation of the lubricating oil may be ashless or ash-forming in nature. Preferably, the dispersant is ashless. So-called ashless dispersants are organic materials that form substantially no ash upon combustion. For example, non-metal-containing or borated metal-free dispersants are considered ashless. In contrast, metal-containing detergents discussed above form ash upon combustion.

Suitable dispersants typically contain a polar group attached to a relatively high molecular weight hydrocarbon chain. The polar group typically contains at least one element of nitrogen, oxygen, or phosphorus. Typical hydrocarbon chains contain 50 to 400 carbon atoms.

Chemically, many dispersants may be characterized as phenates, sulfonates, sulfurized phenates, salicylates, naphthenates, stearates, carbamates, thiocarbamates, phosphorus derivatives. A particularly useful class of dispersants are the alkenylsuccinic derivatives, typically produced by the reaction of a long chain hydrocarbyl substituted succinic compound, usually a hydrocarbyl substituted succinic anhydride, with a polyhydroxy or polyamino compound. The long chain hydrocarbyl group constituting the oleophilic portion of the molecule which confers solubility in the oil, is normally a polyisobutylene group. Many examples of this type of dispersant are well known commercially and in the literature. Exemplary U.S. patents describing such dispersants are U.S. Pat. Nos. 3,172,892; 3,215,707; 3,219,666; 3,316,177; 3,341,542; 3,444,170; 3,454,607; 3,541,012; 3,630,904; 3,632,511; 3,787,374 and 4,234,435. Other types of dispersant are described in U.S. Pat. Nos. 3,036,003; 3,200,107; 3,254,025; 3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,413,347; 3,697,574; 3,725,277; 3,725,480; 3,726,882; 4,454,059; 3,329,658; 3,449,250; 3,519,565; 3,666,730; 3,687,849; 3,702,300; 4,100,082; 5,705,458. A further description of dispersants may be found, for example, in European Patent Application No. 471 071, to which reference is made for this purpose.

Hydrocarbyl-substituted succinic acid and hydrocarbyl-substituted succinic anhydride derivatives are useful dispersants. In particular, succinimide, succinate esters, or succinate ester amides prepared by the reaction of a hydrocarbon-substituted succinic acid compound preferably having at least 50 carbon atoms in the hydrocarbon substituent, with at least one equivalent of an alkylene amine are particularly useful.

Succinimides are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and amines. Molar ratios can vary depending on the polyamine. For example, the molar ratio of hydrocarbyl substituted succinic anhydride to TEPA can vary from 1:1 to 5:1. Representative examples are shown in U.S. Pat. Nos. 3,087,936; 3,172,892; 3,219,666; 3,272,746; 3,322,670; and 3,652,616, 3,948,800; and Canada Patent No. 1,094,044.

Succinate esters are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and alcohols or polyols. Molar ratios can vary depending on the alcohol or polyol used. For example, the condensation product of a hydrocarbyl substituted succinic anhydride and pentaerythritol is a useful dispersant.

Succinate ester amides are formed by condensation reaction between hydrocarbyl substituted succinic anhydrides and alkanol amines. For example, suitable alkanol amines include ethoxylated polyalkylpolyamines, propoxylated polyalkylpolyamines and polyalkenylpolyamines such as polyethylene polyamines. One example is propoxylated hexamethylenediamine. Representative examples are shown in U.S. Pat. No. 4,426,305.

The molecular weight of the hydrocarbyl substituted succinic anhydrides used in the preceding paragraphs will typically range between 800 and 2,500. The above products can be post-reacted with various reagents such as sulfur, oxygen, formaldehyde, carboxylic acids such as oleic acid. The above products can also be post reacted with boron compounds such as boric acid, borate esters or highly borated dispersants, to form borated dispersants generally having from 0.1 to 5 moles of boron per mole of dispersant reaction product.

Mannich base dispersants are made from the reaction of alkylphenols, formaldehyde, and amines. See U.S. Pat. No. 4,767,551, which is incorporated herein by reference. Process aids and catalysts, such as oleic acid and sulfonic acids, can also be part of the reaction mixture. Molecular weights of the alkylphenols range from 800 to 2,500. Representative examples are shown in U.S. Pat. Nos. 3,697,574; 3,703,536; 3,704,308; 3,751,365; 3,756,953; 3,798,165; and 3,803,039.

Typical high molecular weight aliphatic acid modified Mannich condensation products useful in this disclosure can be prepared from high molecular weight alkyl-substituted hydroxyaromatics or HN®₂ group-containing reactants.

Hydrocarbyl substituted amine ashless dispersant additives are well known to one skilled in the art; see, for example, U.S. Pat. Nos. 3,275,554; 3,438,757; 3,565,804; 3,755,433, 3,822,209, and 5,084,197.

Preferred dispersants include borated and non-borated succinimides, including those derivatives from mono-succinimides, bis-succinimides, and/or mixtures of mono- and bis-succinimides, wherein the hydrocarbyl succinimide is derived from a hydrocarbylene group such as polyisobutylene having a Mn of from 500 to 5000 or a mixture of such hydrocarbylene groups. Other preferred dispersants include succinic acid-esters and amides, alkylphenol-polyamine-coupled Mannich adducts, their capped derivatives, and other related components. A preferred dispersant is polyisobutylene succinimide polyamine (PIBSA-PAM). Such additives may be used in an amount of 0.1 to 20 weight percent, preferably 0.5 to 8 weight percent.

Detergents

A typical detergent is an anionic material that contains a long chain hydrophobic portion of the molecule and a smaller anionic or oleophobic hydrophilic portion of the molecule. The anionic portion of the detergent is typically derived from an organic acid such as a sulfur acid, carboxylic acid, phosphorous acid, phenol, or mixtures thereof. The counterion is typically an alkaline earth or alkali metal.

Salts that contain a substantially stochiometric amount of the metal are described as neutral salts and have a total base number (TBN, as measured by ASTM D2896) of from 0 to 80. Many compositions are overbased, containing large amounts of a metal base that is achieved by reacting an excess of a metal compound (a metal hydroxide or oxide, for example) with an acidic gas (such as carbon dioxide). Useful detergents can be neutral, mildly overbased, or highly overbased.

It is desirable for at least some detergent to be overbased. Overbased detergents help neutralize acidic impurities produced by the combustion process and become entrapped in the oil. Typically, the overbased material has a ratio of metallic ion to anionic portion of the detergent of 1.05:1 to 50:1 on an equivalent basis. More preferably, the ratio is from 4:1 to 25:1. The resulting detergent is an overbased detergent that will typically have a TBN of 150 or higher, often 250 to 450 or more. Preferably, the overbasing cation is sodium, calcium, or magnesium. A mixture of detergents of differing TBN can be used in the present disclosure.

Preferred detergents include the alkali or alkaline earth metal salts of sulfonates, phenates, carboxylates, phosphates, and salicylates, e.g., a mixture of magnesium sulfonate and calcium salicylate.

Sulfonates may be prepared from sulfonic acids that are typically obtained by sulfonation of alkyl substituted aromatic hydrocarbons. Hydrocarbon examples include those obtained by alkylating benzene, toluene, xylene, naphthalene, biphenyl and their halogenated derivatives (chlorobenzene, chlorotoluene, and chloronaphthalene, for example). The alkylating agents typically have 3 to 70 carbon atoms. The alkaryl sulfonates typically contain 9 to 80 carbon or more carbon atoms, more typically from 16 to 60 carbon atoms.

Alkaline earth phenates are another useful class of detergent. These detergents can be made by reacting alkaline earth metal hydroxide or oxide (CaO, Ca(OH)₂, BaO, Ba(OH)₂, MgO, Mg(OH)₂, for example) with an alkyl phenol or sulfurized alkylphenol. Useful alkyl groups include straight chain or branched C₁-C₃₀ alkyl groups, preferably, C₄-C₂₀. Examples of suitable phenols include isobutylphenol, 2-ethylhexylphenol, nonylphenol, dodecyl phenol, and the like. It should be noted that starting alkylphenols may contain more than one alkyl substituent that are each independently straight chain or branched. When a non-sulfurized alkylphenol is used, the sulfurized product may be obtained by methods well known in the art. These methods include heating a mixture of alkylphenol and sulfurizing agent (including elemental sulfur, sulfur halides such as sulfur dichloride, and the like) and then reacting the sulfurized phenol with an alkaline earth metal base.

Metal salts of carboxylic acids are also useful as detergents. These carboxylic acid detergents may be prepared by reacting a basic metal compound with at least one carboxylic acid and removing free water from the reaction product. These compounds may be overbased to produce the desired TBN level. Detergents made from salicylic acid are one preferred class of detergents derived from carboxylic acids. Useful salicylates include long chain alkyl salicylates. One useful family of compositions is of the formula

where R is an alkyl group having 1 to 30 carbon atoms, n is an integer from 1 to 4, and M is an alkaline earth metal. Preferred R groups are alkyl chains of at least C₁₁, preferably C₁₃ or greater. R may be optionally substituted with substituents that do not interfere with the detergent's function. M is preferably, calcium, magnesium, or barium. More preferably, M is calcium.

Hydrocarbyl-substituted salicylic acids may be prepared from phenols by the Kolbe reaction (see U.S. Pat. No. 3,595,791). The metal salts of the hydrocarbyl-substituted salicylic acids may be prepared by double decomposition of a metal salt in a polar solvent such as water or alcohol.

Alkaline earth metal phosphates are also used as detergents and are known in the art.

Detergents may be simple detergents or what is known as hybrid or complex detergents. The latter detergents can provide the properties of two detergents without the need to blend separate materials. See U.S. Pat. No. 6,034,039.

Preferred detergents include calcium phenates, calcium sulfonates, calcium salicylates, magnesium phenates, magnesium sulfonates, magnesium salicylates and other related components (including borated detergents) in any combination. A preferred detergent includes magnesium sulfonate and calcium salicylate.

The detergent concentration in the lubricating oils of this disclosure can range from 1.0 to 6.0 weight percent, preferably 2.0 to 5.0 weight percent, and more preferably from 2.0 weight percent to 4.0 weight percent, based on the total weight of the lubricating oil.

Anti-Wear Additives

A metal alkylthiophosphate and more particularly a metal dialkyl dithio phosphate in which the metal constituent is zinc, or zinc dialkyl dithio phosphate (ZDDP) is a component of the lubricating oils of this disclosure. ZDDP can be primary, secondary or mixtures thereof. ZDDP compounds generally are of the formula Zn[SP(S)(OR¹)(OR²)]₂ where R¹ and R² are C₁-C₁₈ alkyl groups, preferably C₂-C₁₂ alkyl groups. These alkyl groups may be straight chain or branched.

Preferable zinc dithiophosphates which are commercially available include secondary zinc dithiophosphates such as those available from for example, The Lubrizol Corporation under the trade designations “LZ 677A”, “LZ 1095” and “LZ 1371”, from for example Chevron Oronite under the trade designation “OLOA 262” and from for example Afton Chemical under the trade designation “HITEC 7169”.

The ZDDP is typically used in amounts of from 0.4 weight percent to 1.2 weight percent, preferably from 0.5 weight percent to 1.0 weight percent, and more preferably from 0.6 weight percent to 0.8 weight percent, based on the total weight of the lubricating oil, although more or less can often be used advantageously. Preferably, the ZDDP is a secondary ZDDP and present in an amount of from 0.6 to 1.0 weight percent of the total weight of the lubricating oil.

ZDDP is one of the most successful anti-wear additives ever used in lubricants. This additive is fairly cost effective and provides exceptionally durable anti-wear tribofilms on ferrous surfaces under extreme lubrication conditions. ZDDP forms protective films on ferrous surfaces within a very short period of time. This additive forms pad-like polymeric tribofilms at the rubbing contact and thus prevents wear. It is believed that ZDDP undergoes thermal decomposition at the tribological contact followed by the reactions with reactive iron surfaces or iron oxides that forms glassy phosphate films. These films contain minimal iron meaning that the formation of tribofilm requires minimal loss of iron from the rubbed surfaces. The chain lengths of the phosphate decreases with the depth of the tribofilm and the layers near the surface were mostly dominated by iron sulphides and iron oxides.

Using an optical interferometry technique, it has been demonstrated that the formation of ZDDP tribofilm takes several tens of minutes. The friction coefficients during the film formation period initially increases and then gradually decreases and finally reaches to steady state. The increase of friction is a result of initial wear (adhesive/abrasive wear) that generates enough nascent iron to react with the thermally decomposed ZDDP. As soon as the ZDDP tribofilm starts to dominate the contact between two interacting surfaces, friction starts to decrease. Since the film formation of ZDDP is primarily influenced by the initial wear, the nature of wear influences the uniformity as well as growth rate of ZDDP tribofilm to a great extent.

Uniform anti-wear tribofilms are desirable over the non-uniform patchy tribofilms. This is because the uniform tribofilm can resist the applied load more uniformly and thereby generates distributed stresses within the tribofilm. In contrast, in the case of non-uniform tribofilms, the applied load is mainly taken by the high spots resulting in more concentrated stresses and thereby causing more failure of tribofilms. This disclosure reveals that NGP materials enable the formation of uniform ZDDP tribofilms by controlling the initial wear process.

Pour Point Depressants (PPDs)

Conventional pour point depressants (also known as lube oil flow improvers) may be added to the compositions of the present disclosure if desired. These pour point depressant may be added to lubricating compositions of the present disclosure to lower the minimum temperature at which the fluid will flow or can be poured. Examples of suitable pour point depressants include polymethacrylates, polyacrylates, polyarylamides, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, and terpolymers of dialkylfumarates, vinyl esters of fatty acids and allyl vinyl ethers. U.S. Pat. Nos. 1,815,022; 2,015,748; 2,191,498; 2,387,501; 2,655, 479; 2,666,746; 2,721,877; 2,721,878; and 3,250,715 describe useful pour point depressants and/or the preparation thereof. Such additives may be used in an amount of 0.01 to 5 weight percent, preferably 0.01 to 1.5 weight percent.

Seal Compatibility Agents

Seal compatibility agents help to swell elastomeric seals by causing a chemical reaction in the fluid or physical change in the elastomer. Suitable seal compatibility agents for lubricating oils include organic phosphates, aromatic esters, aromatic hydrocarbons, esters (butylbenzyl phthalate, for example), and polybutenyl succinic anhydride. Such additives may be used in an amount of 0.01 to 3 weight percent, preferably 0.01 to 2 weight percent.

Antifoam Agents

Anti-foam agents may advantageously be added to lubricant compositions. These agents retard the formation of stable foams. Silicones and organic polymers are typical anti-foam agents. For example, polysiloxanes, such as silicon oil or polydimethyl siloxane, provide antifoam properties. Anti-foam agents are commercially available and may be used in conventional minor amounts along with other additives such as demulsifiers; usually the amount of these additives combined is less than 1 weight percent and often less than 0.1 weight percent.

Viscosity Index Improvers

Viscosity index improvers (also known as VI improvers, viscosity modifiers, and viscosity improvers) can be included in the lubricant compositions of this disclosure. Preferably, the method of this disclosure obtains improvements in fuel economy without sacrificing durability by a reduction of high-temperature high-shear (HTHS) viscosity to a level lower than 2.6 cP through reduction or removal of viscosity index improvers or modifiers.

Viscosity index improvers provide lubricants with high and low temperature operability. These additives impart shear stability at elevated temperatures and acceptable viscosity at low temperatures.

Suitable viscosity index improvers include high molecular weight hydrocarbons, polyesters and viscosity index improver dispersants that function as both a viscosity index improver and a dispersant. Typical molecular weights of these polymers are between 10,000 to 1,500,000, more typically 20,000 to 1,200,000, and even more typically between 50,000 and 1,000,000.

Examples of suitable viscosity index improvers are linear or star-shaped polymers and copolymers of methacrylate, butadiene, olefins, or alkylated styrenes. Polyisobutylene is a commonly used viscosity index improver. Another suitable viscosity index improver is polymethacrylate (copolymers of various chain length alkyl methacrylates, for example), some formulations of which also serve as pour point depressants. Other suitable viscosity index improvers include copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, and polyacrylates (copolymers of various chain length acrylates, for example). Specific examples include styrene-isoprene or styrene-butadiene based polymers of 50,000 to 200,000 molecular weight.

Olefin copolymers, are commercially available from Chevron Oronite Company LLC under the trade designation “PARATONE®” (such as “PARATONE® 8921” and “PARATONE® 8941”); from Afton Chemical Corporation under the trade designation “HiTEC®” (such as “HiTEC® 5850B”; and from The Lubrizol Corporation under the trade designation “Lubrizol® 7067C”. Polyisoprene polymers are commercially available from Infineum International Limited, e.g. under the trade designation “SV200”; diene-styrene copolymers are commercially available from Infineum International Limited, e.g. under the trade designation “SV 260”.

In an embodiment of this disclosure, the viscosity index improvers may be used in an amount of less than 2.0 weight percent, preferably less than 1.0 weight percent, and more preferably less than 0.5 weight percent, based on the total weight of the formulated oil or lubricating engine oil.

In another embodiment of this disclosure, the viscosity index improvers may be used in an amount of from 0.0 to 2.0 weight percent, preferably 0.0 to 1.0 weight percent, and more preferably 0.0 to 0.5 weight percent, based on the total weight of the formulated oil or lubricating engine oil.

When lubricating oil compositions contain one or more of the additives discussed above, the additive(s) are blended into the composition in an amount sufficient for it to perform its intended function. Typical amounts of such additives useful in the present disclosure are shown in Table A below.

It is noted that many of the additives are shipped from the additive manufacturer as a concentrate, containing one or more additives together, with a certain amount of base oil diluents. Accordingly, the weight amounts in the table below, as well as other amounts mentioned in this specification, are directed to the amount of active ingredient (that is the non-diluent portion of the ingredient). The weight percent (wt %) indicated below is based on the total weight of the lubricating oil composition.

TABLE 1 Typical Amounts of Other Lubricating Oil Components Approximate Approximate Compound wt % (Useful) wt % (Preferred) Dispersant  0.1-20 0.1-8  Detergent  1.0-6.0  2.0-4.0 Friction Modifier 0.01-5  0.01-1.5 Antioxidant 0.1-5  0.1-1.5 Pour Point Depressant 0.0-5 0.01-1.5 (PPD) Anti-foam Agent 0.001-3  0.001-0.15 Viscosity Index Improver 0.0-2 0.0-1  (solid polymer basis)

The foregoing additives are all commercially available materials. These additives may be added independently but are usually precombined in packages which can be obtained from suppliers of lubricant oil additives. Additive packages with a variety of ingredients, proportions and characteristics are available and selection of the appropriate package will take the requisite use of the ultimate composition into account.

The following non-limiting examples are provided to illustrate the disclosure.

EXAMPLES Description of CMC Method

The treat rate of the surfactant should be greater than or equal to the critical micelle concentration of that surfactant in the base oil. Critical micelle concentration (CMC) of a surfactant was determined using interfacial tension (IFT) measurements over a range of surfactant concentrations. IFT values were averaged over 10 minutes in an equilibrium system of an 18 Mohm H₂O droplet suspended in a solution of ‘X’ wt % surfactant in a base oil where ‘X’ is a range of surfactant concentrations. The measurements were repeated 4 times, such that the IFT value for a given concentration was the average of 4 measurements. The CMC of the surfactant was then determined from a plot of the averaged IFT values against the natural logarithm of the surfactant concentration, by identifying the concentration at which an abrupt change in slope was observed.

Example 1

FIGS. 1-4 show the film forming properties of ammonium tetrathiomolybdate dissolved in tetraethylene glycol and dispersed as swollen inverse micelles in Spectrasyn®-4 (referred to as NB:25417-145-3 in FIGS. 1-4). The ammonium tetrathiomolybdate was first dissolved in tetraethylene glycol and the resulting product was added to Spectrasyn®-4 under low shear mixing followed by high shear mixing. Spectrasyn®-4 is a commercially available metallocene polyalphaolefin (mPAO). The data shown in FIGS. 1-4 was taken using an elastohydrodynamic lubrication (EHL) instrument (PCS Instruments, London, UK) at 40° C., 60° C., 80° C. and 100° C. The NB:25417-145-3 swollen inverse micelle system was compared to Spectrasyn®-4 alone as a control, and also a commercially available premium synthetic 0W-20 fully formulated motor oil.

The composition of the swollen inverse micelle system NB:25417-145-3 was as follows:

2% Dispersed Phase—5% ammonium tetrathiomolybdate dissolved in tetraethylene glycol 98% Continuous Phase—9% PIBSA-PAM (polyisobutylene succinimide polyamine) surfactant in PAO4.

FIG. 1 graphically depicts the EHL measurement of film thickness at 40° C. of the NB:25417-145-3 swollen inverse micelle system, Spectrasyn®-4, and premium synthetic 0W-20 motor oil. The inverse micelle system provides exceptional EHL friction benefits at low speeds. This characteristic is very important for motor oils because oil films break down at low speeds resulting in metal-metal contact.

FIG. 2 graphically depicts the EHL measurement of film thickness at 60° C. of the NB:25417-145-3 swollen inverse micelle system, Spectrasyn®-4, and premium synthetic 0W-20 motor oil. The inverse micelle system maintains exceptional EHL friction benefits at low speeds as the temperature is increased from 40° C. to 60° C.

FIG. 3 graphically depicts the EHL measurement of film thickness at 80° C. of the NB:25417-145-3 swollen inverse micelle system, Spectrasyn®-4, and premium synthetic 0W-20 motor oil. The inverse micelle system maintains significantly higher EHL lubrication as temperature increases to 80° C.

FIG. 4 graphically depicts the EHL measurement of film thickness at 100° C. of the NB:25417-145-3 swollen inverse micelle system, Spectrasyn®-4, and premium synthetic 0W-20 motor oil. The At highest temperature (100° C.), the inverse micelle system surprisingly shows exceptional EHL lubrication relative to a premium synthetic motor oil as well as a synthetic base-stock.

The swollen inverse micelle system NB:25417-145-3 shows superior retention of film thickness as a function of temperature compared to the control (i.e., Spectrasyn®-4) and a premium synthetic 0W-20 motor oil fully formulated motor oil having no swollen inverse micelle system.

Example 2

The above system NB:25417-145-3 was further stabilized by forming a polymer film at the interface of the two phases. This was achieved by dissolving in the polar dispersed phase a high molecular weight polymer (i.e., polystyrene sulfonic acid (or salt)) that reacted at the interface with the polyamine head of the surfactant (i.e., PIBSA-PAM (polyisobutylene succinimide polyamine)) molecule.

The composition of the system NB:25417-145-3 was as follows:

2% Dispersed Phase—1% polystyrene sulfonic acid (or salt) 5% ammonium tetrathiomolybdate dissolved in tetraethylene glycol 98% Continuous Phase—9% PIBSA-PAM (polyisobutylene succinimide polyamine) surfactant in PAO4

Example 3

FIG. 5 shows friction versus temperature comparisons for ammonium tetrathiomolybdate and for swollen inverse micelle systems containing ammonium tetrathiomolybdate. The device used for the comparisons was a High Frequency Reciprocating Rig (HFRR) manufactured by PCS Instruments, London, UK. Friction data was collected while ramping temperature from 25° C. to 200° C. In FIG. 5, the blue line is PAO4 base stock as a control. The green line is PAO4 base stock with polyisobutylene succinimide polyamine (PIBSA-PAM) surfactant as a control. This is the external or continuous phase of the swollen inverse micelle system. The turquoise line is ammonium tetrathiomolybdate (NH₄)₂MoS₄ and MoSO₄(NH₄)₂ contained in the swollen inverse micelle system of this disclosure. The purple line is tetraethylene glycol (Set 2) which is the polar core solvent. The pink line is ammonium tetrathiomolybdate (NH₄)₂MoS₄ dissolved in tetraethylene glycol (Set 2) (i.e., polar core with dissolved friction modifier). The yellow line is molybdenum disulfide (MoS₂ solid) (Set 2) dispersed in PAO4. Ammonium tetrathiomolybdate decomposes to molybdenum disulfide at high temperatures. The red line is another tetraethylene glycol control for the polar core. The turquoise line and pink line clearly show the benefit of the ammonium tetrathiomolybdate friction modifier in the polar core solvent and contained in the swollen inverse micelle systems in PAO4. The swollen inverse micelle system enables the additive to be dispersed in PAO4 in invisible sub-micron micelles. The swollen inverse micelle system also showed the best friction reduction at the highest test temperature (200° C.).

FIG. 5 graphically depicts friction versus temperature comparisons for ammonium tetrathiomolybdate including base stock control, surfactant control and tetraethylene glycol control (with swollen inverse micelles and without swollen inverse micelles). The inverse micelle system enables inorganic friction modifiers to be solubilized in motor oil which is predominately hydrophobic and contains nonpolar base stocks as the primary constituent. The inverse micelle system protects the inorganic friction modifier at high temperatures (150° C. to 200° C.+) which are typical of engine cylinder liners and ring zones. Note the improving performance for the inverse micelle protected (NH4)2MoS4* at 200° C. Above data is obtained with the HFRR. It is designed to test boundary friction in which metal-metal contact occurs. This type of friction is characteristic of piston ring contact with engine cylinder liner surfaces. The HFRR conditions: included a temperature of 25° C. to 200° C. ramp; a load of 400 g; and a reciprocating frequency of 60 Hz.

FIG. 6 shows a model swollen inverse micelle system, i.e., tetraethylene glycol, with a dissolved additive, i.e., ammonium tetrathiomolybdate, dispersed within a lubricant, i.e., PAO4. The layer of the surfactant molecules according to this disclosure can further be formed of polymers of polystyrene sulfonic acid (or salt). PIBSA-PAM is a surfactant useful in this disclosure.

The inverse micelle system was formed by first dissolving the inorganic ammonium tetrathiomolybdate (friction modifier) in a polar solvent (i.e., tetraethylene glycol). This solution was then dispersed in a base stock containing a surfactant. A polyisobutylene succinic anhydride (PIBSA) was reacted with a polyamine that was used as the surfactant to form the inverse micelle shell. The polyamine which was attached to this oil soluble PIBSA surfactant was very polar and oriented itself around the dissolved inorganic molybdate/glycol solution.

FIG. 7 shows the measurement of micelle size using a Horiba LA910 laser light scattering particle size analyzer. The device measured a mean particle size of 0.096 microns for the swollen inverse micelle system. The swollen inverse micelle system according to this disclosure is unique relative to typical emulsions in that the inverse micellar compositions can be infinitely diluted without coalescence. Particles of this size are not visible (completely clear), but are larger than a typical micro emulsion which is in the range of 5 to 200 nm.

The laser light scattering measurement of the inverse micelle particle size distribution showed an optimal mean diameter of 0.082 micron. Very small particle size results in optically clear dispersions of the inverse micelles in the motor oil or other lubricant.

FIG. 8 is a 100× objective photograph of a macrocapsule (without polymer film) of polystyrene sulfonic acid (sodium salt) dissolved in tetraethylene glycol that is dispersed in oil without a surfactant. FIG. 9 is a 100× objective photograph of a swollen inverse micelle (with polymer film) of polystyrene sulfonic acid (sodium salt) dissolved in tetraethylene glycol that is dispersed in oil with a surfactant (i.e., PIBSA-PAM). The photographs are macrocapsules (FIG. 8) and swollen inverse micelles (FIG. 9) formed using very low shear to make them visible by optical microscopy. The friction and EHL data set forth herein was generated without a polymer film.

In FIG. 8, at low shear the polar solvent with a dissolved additive can be seen optically (with a microscope at 100× magnification) dispersed in the nonpolar lubricant.

In FIG. 9, a PIBSA-PAM formed inverse micelle is further stabilized by cross-linking the polar polyamine head group with a high molecular weight polymer salt. A one million molecular weight polystyrene sulfonic acid cross links the polyamine to form an interfacial polymer film. This stabilization step is optional and not necessary for motor oil applications, but may be applied for other uses of this technology.

Example 4

Formulations were prepared as set forth in FIG. 10. This example tests the hypothesis that an antioxidant contained in a swollen inverse micelle system provides sustained protection against oxidation relative to a control (i.e., an antioxidant not contained in a swollen inverse micelle system). The antioxidant tested was diphenylamine (DPA) and it was tested both inside the swollen inverse micelle system and dissolved in a co-base stock without the swollen inverse micelle system. Both were compared in a bench oxidation test simulating a 100 hour engine test with samples taken at intervals to measure degree of oxidation as a function of time. The results shown in FIG. 11 show DPA concentration indicated by the infrared absorbance of the aminic group as the lubricant is oxidized (i.e., Fourier Transform Infrared Spectroscopy (FTIR)). The FTIR oxidation test shows that inverse micellization of an antioxidant along with a friction modifier (shown in green) retains active antioxidant throughout the test. The result in red shows a similar retention of antioxidant for an antioxidant on its own contained in an inverse micelle. The control of an antioxidant not contained in an inverse micelle in blue shows approximately 50% depletion over the same test period.

In FIG. 11, the inverse micelle system provides protection to diphenylamine (DPA) antioxidant, which results in lower oxidation as indicated by slower growth in FTIR carbonyl as a function of time in a custom designed oxidation test. The FTIR oxidation test conditions were a temperature of 150° C., an air flow rate of 120 cc/min., a catalyst—40 ppm Fe+3, and a sample size of 11 g.

In FIG. 12, the same sample series as above were measured by FTIR for oxidation by infrared carbonyl absorbance as a function of time in the oxidation test. The results clearly show that the two inverse micellization samples with and without friction modifier (green and red) showed less of an increase in oxidation than the control (in blue) having no inverse micellization.

In FIG. 12, the inverse micelle system provides protection to diphenylamine (DPA) antioxidant, which results in higher retention of the antioxidant as indicated by slower depletion of NH functional group by FTIR absorbance as a function of time in a custom designed oxidation test. The FTIR oxidation test conditions were a temperature of 150° C., an air flow rate of 120 cc/min., a catalyst—40 ppm Fe+3, and a sample size of 11 g.

This example shows sustained antioxidant protection in a lubricating oil by utilizing one or more antioxidants in a swollen inverse micelle system. This example also shows extended low friction benefits from a friction modifier, as a lubricating oil ages, through the inverse micellization of both the friction modifier and one or more antioxidants. This inverse micellar system provides a protective barrier to isolate the antioxidant from competing chemical reactions with other additives. This inverse micellar system also provides protection from the harmful effects of oxidation on friction modifier performance.

Example 5

Formulations were prepared as set forth in FIG. 13. Referring to FIG. 14, this example shows the benefit of an inorganic molybdate friction modifier contained in an inverse micelle system (in blue) compared to a state of the art premium synthetic lubricant (in red) containing 0.15% of an organometallic friction modifier and not contained in an inverse micelle system, in lowering friction in a High Frequency Reciprocating Rig (HFRR) boundary lubricity test. FIG. 14 also shows (in green) the synergy of combining the organometallic friction modifier not contained in an inverse micelle system and the inorganic molybdate friction modifier contained in an inverse micelle system in a 50/50 mix.

In FIG. 14, the inverse micelle protected inorganic molybdate (NH4)2MoS4 shows lower boundary friction than conventional organometallic friction modifiers such as molybdenum dithiocarbamates. Surprising, synergy results when the inorganic and organometallic molybdenum friction modifiers are used in combination. This synergy results in very low friction. The HFRR conditions were a temperature of 150° C. isothermal, a load of 400 g (translates to a 1 GPa Herzian contact), and a reciprocating frequency of 60 Hz.

Referring to FIG. 15, this example shows the benefit of the mixture of molybdenum additives in a formulation (i.e., an inorganic molybdate friction modifier contained in an inverse micelle system and an organometallic friction modifier not contained in an inverse micelle system), compared to a state of the art premium synthetic lubricant containing 0.15% (in red) and 0.3% (in purple) of an organometallic friction modifier not contained in an inverse micelle system. This comparison was made using the Mini-Traction Machine (MTM) manufactured by PCS Instruments which shows traction coefficient as a function of speed. The mixture of molybdenum additives shows significantly better performance in the boundary, mixed and hydrodynamic lubricating regimes.

In FIG. 15, a Stribeck curve format is shown for friction data obtained with the Mini-Traction Machine (MTM). It is designed to test boundary (metal-metal contact), hydrodynamic (full lubricating film) and mixed friction regimes. The inverse micelle protected inorganic molybdate (NH4)2MoS4 shows lower traction coefficient than conventional organometallic friction modifiers such as molybdenum dithiocarbamates. Surprising synergy was seen when the inorganic and organometallic molybdenum friction modifiers were used in combination. This synergy results in very low traction coefficients which translates to lower friction. This is a desired benefit seen in boundary and mixed lubrication regime in the MTM. The smoother transition for the inverse micelle from boundary to hydrodynamic is shown at MTM conditions including a temperature of 100° C. isothermal and a load of 1 GPa.

Referring to FIG. 16, this example shows the results of engine tests conducted on the mixture of molybdenum additives in a formulation (i.e., an inorganic molybdate friction modifier contained in an inverse micelle system and an organometallic friction modifier not contained in an inverse micelle system) compared to a premium GF-5 state of the art synthetic motor oil. The mixture of molybdenum additives showed improved initial fuel economy in both the industry standard Sequence VI-D and Sequence VI-E engine tests.

This example shows improved low friction performance of a lubricating oil with an inorganic molybdate friction modifier contained in an inverse micelle system with or without an organometallic friction modifier.

This example also shows improved solubility of an inorganic molybdate friction modifier by dissolving in a polar solvent in an inverse micelle. This example demonstrates that the inorganic molybdate friction modifier contained in an inverse micelle system reduces friction to a greater extent than standard organometallic molybdenum friction modifiers not contained in an inverse micelle system. This example also shows a synergistic friction reducing benefit of combining the inorganic molybdate in the inverse micelle system with an organometallic molybdate dissolved in the lubricant continuous phase, that results in an even greater reduction of friction than either friction modifier singly.

This example further shows that the inorganic molybdate friction modifier contained in an inverse micelle system and the mixture of the inorganic molybdate friction modifier in the inverse micelle system and the organometallic molybdate friction modifier not in an inverse micelle system provides a significant friction benefit over a current premium synthetic motor oil formulation containing only a organometallic friction modifier as demonstrated through a lower frictional coefficient in a bench test (FIG. 12). This example also shows that the mixture of the inorganic molybdate friction modifier in the inverse micelle system and the organometallic molybdate friction modifier not in an inverse micelle system provides improved frictional performance over each of the individual friction modifiers contained in this system, demonstrating a synergistic effect. This example further shows that the mixture of the inorganic molybdate friction modifier in the inverse micelle system and the organometallic molybdate friction modifier not in an inverse micelle system provides a benefit for fresh oil fuel economy relative to a current premium synthetic motor oil formulation as tested in industry standard engine tests.

In FIG. 16, the engine test data is from two industry standard fuel economy measurements. ASTM D7589 is a standard test method for measurement of effects of automotive engine oils on fuel economy of passenger cars and light-duty trucks in sequence VI-D (current GF-5 ILSAC rating) and VI-E (next generation GF-6 rating) spark ignition engines. The inverse micelle protected inorganic molybdate (NH4)2MoS4 in combination with organometallic Mo-trimer shows better fuel economy in both the VI-D and VI-E engine tests. Surprisingly, better fuel economy is shown in the VI-E engine for the inverse micelle protected inorganic/organometallic molybdate combination, considering its higher viscosity (0W-20) compared to the premium synthetic comparison (0W-16). The lower viscosity of the premium synthetic would give it a fuel economy edge.

Example 6

This example shows that the inverse micelles are stable at high shear conditions. Under high shear conditions, the inverse micelles are self-healing and reform to smaller diameter spheres.

FIG. 17 shows that the inverse micelles are stable at high shear conditions and that under high shear conditions, the inverse micelles are self-healing and reform to smaller diameter spheres. Also, FIG. 17 shows the high shear conditions needed to obtain optical clarity (e.g., inverse micelle mean diameter below about 0.4 μm).

FIG. 17 shows increased shear using mechanical mixers compared to microfluidizer. A low shear mixing using magnetic stirring of 100 ml volume in a 250 ml beaker; standard Corning stirrer and 5 mm×50 mm magnetic stir bar has a shear rate of about 1000 sec.-1. A high shear mixing using a IKA T25 TURRAX rotor-stator at 20,000 RPM of 50 ml volume in a 100 ml tall form wide mouth glass bottle has a shear rate of about 500,000 sec.-1. The ultra-high shear using the microfluidizer with a static interaction chamber has a shear rate of about 10,000,000 sec.-1.

A microfluidizer is preferred for obtaining formulations having optical clarity (e.g., inverse micelle mean diameter below about 0.4 μm). An illustrative microfluidizer is shown in FIG. 18. The microfluidizer draws fluid from the reservoir and pushes it through an interaction chamber at about 40,000 psi. The interaction chamber splits the fluid stream through micro-channels that impinge on each other, creating very high shear rates. The sheared fluid stream is deposited in an open container that has optional cooling. Intense energy creates heat in the interaction chamber.

As shown in FIG. 19, microfluidizers afford higher shear rates than conventional mechanical mixers. Higher shear rates are obtained with a microfluidizer beyond the capability of mechanical mixers.

Also, as shown in FIG. 20, microfluidizers give a more uniform dispersion of particle size. The microfluidizer results in mono-dispersed particles with very low particle size in comparison to conventional high shear mixers which use mechanical blades and high speeds. The Microfluidizer results in a narrower particle size distribution than the high shear mixer.

FIG. 21 shows an optimum inverse micelle diameter after high shear conditions in a microfluidizer (e.g., 0.082 μm mean diameter). The microfluidizer results in 0.082 mean particle size, and optically clear dispersions of glycol solubilized inorganic molybdate (NH4)2MoS4.

FIG. 22 shows that reducing the inverse micelle diameter size from 0.2 μm to 0.1 μm shows benefit with regard to coefficient of friction. In particular, reducing the inverse micelle size reduces friction resulting in improved boundary friction performance in the HFRR. The HFRR test conditions were a temperature of 150° C., a load of 400 g (translates to a 1 GPa Herzian contact), and a reciprocating frequency of 60 Hz.

FIG. 23 shows Dynamic Light Scattering (DLS) data for inverse micelle diameter size measurement during engine test. T=0 was larger than typical attributed to a first scale-up. The engine was efficient in reducing inverse micelle diameter size. All samples taken from the engine were between 0.06 μm and 0.07 μm.

In FIG. 23, initial particle size of inverse micelle protected inorganic molybdate (NH4)2MoS4 was sheared to below 0.1 micron in this engine as measured by laser light scattering after initial 16 hours of engine aging. Particle size below 0.1 micron was maintained through the entire engine test of 118 hours. This data demonstrates that the inverse micelle is stable to the engine operating conditions of high temperatures and shear, reforming at a smaller particle size as it is circulated through the engine. Also, this data evidences that the inverse micelle is self-healing.

FIG. 24 shows that inverse micelles are stable to ultrasonic shear. Ultrasonic shear conditions generate high cavitation pressure shock waves and temperatures that would destroy most polymer and wax hard shell capsules.

In FIG. 24, inverse micelle protection of the inorganic molybdate (NH4)2MoS4 was maintained when experiencing ultrasonic shear as indicated by constant particle size. A Horiba LA-910 laser light scattering was used for measurements.

PCT and EP Clauses:

1. A lubricating oil comprising a nonpolar lubricating oil base stock as a major component and one or more polar lubricating oil additives as a minor component; wherein said one or more polar lubricating oil additives comprise swollen inverse micelles dispersed in said nonpolar lubricating oil base stock; and wherein said swollen inverse micelles comprise (i) a liquid polar core containing a polar solvent and one or more polar lubricating oil additives having solubility in said polar solvent, and (ii) a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.

2. The lubricating oil of clause 1 wherein the polar solvent is selected from the group consisting of glycols, alcohols, esters, ethers, carboxylic acids, amines, organic compounds containing one or more polar functional groups, and mixtures thereof.

3. The lubricating oil of clauses 1 and 2 wherein the one or more polar lubricating oil additives are selected from the group consisting of friction modifiers, antioxidants, corrosion inhibitors, rust inhibitors, metal deactivators, anti-wear agents and/or extreme pressure additives, dispersants, detergents, anti-seizure agents, wax modifiers, viscosity index improvers, viscosity modifiers, fluid-loss additives, seal compatibility agents, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, antifoam agents, and pour point depressants.

4. The lubricating oil of clauses 1-3 wherein the surfactant comprises a succinimide, a succinate ester, a succinate ester amide, a hydrocarbyl-substituted succinic acid derivative, a hydrocarbyl-substituted succinic anhydride derivative, an alkenylsuccinic derivative, or mixtures thereof.

5. A method of improving solubility of polar lubricating oil additives in a nonpolar lubricating oil base stock, said method comprising providing a lubricating oil comprising a nonpolar lubricating oil base stock as a major component and one or more polar lubricating oil additives as a minor component; wherein said one or more polar lubricating oil additives comprise swollen inverse micelles dispersed in said nonpolar lubricating oil base stock; and wherein said swollen inverse micelles comprise (i) a liquid polar core containing a polar solvent and one or more polar lubricating oil additives having solubility in said polar solvent, and (ii) a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.

6. The method of clause 5 wherein the polar solvent is selected from the group consisting of glycols, alcohols, esters, ethers, carboxylic acids, amines, organic compounds containing one or more polar functional groups, and mixtures thereof; and wherein the surfactant comprises a succinimide, a succinate ester, a succinate ester amide, a hydrocarbyl-substituted succinic acid derivative, a hydrocarbyl-substituted succinic anhydride derivative, an alkenylsuccinic derivative, or mixtures thereof.

7. The method of clauses 5 and 6 wherein the one or more polar lubricating oil additives are selected from the group consisting of friction modifiers, antioxidants, corrosion inhibitors, rust inhibitors, metal deactivators, anti-wear agents and/or extreme pressure additives, dispersants, detergents, anti-seizure agents, wax modifiers, viscosity index improvers, viscosity modifiers, fluid-loss additives, seal compatibility agents, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, antifoam agents, and pour point depressants.

8. A method of improving surface performance of a lubricating oil in an engine lubricated with the lubricating oil, said method comprising using as the lubricating oil a formulated oil comprising a nonpolar lubricating oil base stock as a major component and one or more polar lubricating oil additives as a minor component; wherein said one or more polar lubricating oil additives comprise swollen inverse micelles dispersed in said nonpolar lubricating oil base stock; and wherein said swollen inverse micelles comprise (i) a liquid polar core containing a polar solvent and one or more polar lubricating oil additives having solubility in said polar solvent, and (ii) a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.

9. The method of clause 8 wherein the polar solvent is selected from the group consisting of glycols, alcohols, esters, ethers, carboxylic acids, amines, organic compounds containing one or more polar functional groups, and mixtures thereof; and wherein the surfactant comprises a succinimide, a succinate ester, a succinate ester amide, a hydrocarbyl-substituted succinic acid derivative, a hydrocarbyl-substituted succinic anhydride derivative, an alkenylsuccinic derivative, or mixtures thereof.

10. The method of clauses 8 and 9 wherein the one or more polar lubricating oil additives are selected from the group consisting of friction modifiers, antioxidants, corrosion inhibitors, rust inhibitors, metal deactivators, anti-wear agents and/or extreme pressure additives, dispersants, detergents, anti-seizure agents, wax modifiers, viscosity index improvers, viscosity modifiers, fluid-loss additives, seal compatibility agents, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, antifoam agents, and pour point depressants.

11. A swollen inverse micelle composition comprising (i) a liquid polar core containing a polar solvent and one or more polar lubricating oil additives having solubility in said polar solvent, and (ii) a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.

12. A process for making a swollen inverse micelle composition, said process comprising:

providing one or more polar lubricating oil additives, a polar solvent, and a surfactant; and

mixing the one or more polar lubricating oil additives, the polar solvent, and the surfactant under conditions sufficient to form the swollen inverse micelle composition;

wherein the swollen inverse micelle composition comprises (i) a liquid polar core containing the polar solvent and the one or more polar lubricating oil additives having solubility in said polar solvent, and (ii) a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.

13. A lubricating oil comprising a nonpolar lubricating oil base stock as a major component and a polar lubricating oil additive as a minor component; wherein said polar lubricating oil additive comprises swollen inverse micelles dispersed in said nonpolar lubricating oil base stock; and wherein said swollen inverse micelles comprise (i) a liquid polar core containing a polar solvent and an antioxidant having solubility in said polar solvent, and (ii) a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.

14. A lubricating oil comprising a nonpolar lubricating oil base stock as a major component and a mixture of polar lubricating oil additives as a minor component; wherein said mixture of polar lubricating oil additives comprises swollen inverse micelles dispersed in said nonpolar lubricating oil base stock; and wherein said mixture of swollen inverse micelles comprises: (a) a liquid polar core containing a polar solvent and an antioxidant having solubility in said polar solvent, and a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core; and (b) a liquid polar core containing a polar solvent and a friction modifier having solubility in said polar solvent, and a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.

15. A lubricating oil comprising a nonpolar lubricating oil base stock as a major component and a mixture of polar lubricating oil additives as a minor component; wherein said mixture of polar lubricating oil additives comprises (a) a first friction modifier comprising an organometallic molybdenum compound, and (b) a second friction modifier comprising swollen inverse micelles dispersed in said nonpolar lubricating oil base stock; wherein said swollen inverse micelles comprises a liquid polar core containing a polar solvent and an inorganic molybdate compound having solubility in said polar solvent, and a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core; and wherein friction reduction and fuel efficiency are maintained or improved as compared to friction reduction and fuel efficiency achieved with a lubricating engine oil using singly the first friction modifier or the second friction modifier, as measured by one or more of ASTM D6079, SEQ VI-D and SEQ VI-E.

All patents and patent applications, test procedures (such as ASTM methods, UL methods, and the like), and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this disclosure and for all jurisdictions in which such incorporation is permitted.

When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated. While the illustrative embodiments of the disclosure have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the disclosure. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present disclosure, including all features which would be treated as equivalents thereof by those skilled in the art to which the disclosure pertains.

The present disclosure has been described above with reference to numerous embodiments and specific examples. Many variations will suggest themselves to those skilled in this art in light of the above detailed description. All such obvious variations are within the full intended scope of the appended claims. 

What is claimed is:
 1. A lubricating oil comprising a nonpolar lubricating oil base stock as a major component and one or more polar lubricating oil additives as a minor component; wherein said one or more polar lubricating oil additives comprise swollen inverse micelles dispersed in said nonpolar lubricating oil base stock; and wherein said swollen inverse micelles comprise (i) a liquid polar core containing a polar solvent and one or more polar lubricating oil additives having solubility in said polar solvent, and (ii) a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.
 2. The lubricating oil of claim 1 wherein the nonpolar lubricating oil base stock comprises a Group I, Group II, Group III, Group IV or Group V base oil.
 3. The lubricating oil of claim 1 wherein the polar solvent is selected from the group consisting of glycols, alcohols, esters, ethers, carboxylic acids, amines, organic compounds containing one or more polar functional groups, and mixtures thereof.
 4. The lubricating oil of claim 1 wherein the one or more polar lubricating oil additives are selected from the group consisting of friction modifiers, antioxidants, corrosion inhibitors, rust inhibitors, metal deactivators, anti-wear agents and/or extreme pressure additives, dispersants, detergents, anti-seizure agents, wax modifiers, viscosity index improvers, viscosity modifiers, fluid-loss additives, seal compatibility agents, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, antifoam agents, and pour point depressants.
 5. The lubricating oil of claim 1 wherein the one or more polar lubricating oil additives comprise one or more friction modifiers, antioxidants, corrosion inhibitors, rust inhibitors, or mixtures thereof.
 6. The lubricating oil of claim 1 wherein the surfactant comprises a succinimide, a succinate ester, a succinate ester amide, a hydrocarbyl-substituted succinic acid derivative, a hydrocarbyl-substituted succinic anhydride derivative, an alkenylsuccinic derivative, or mixtures thereof.
 7. The lubricating oil of claim 1 wherein the surfactant comprises a succinate ester, a phenate, a sulfonate, a sulfurized phenate, a salicylate, a naphthenate, a stearate, a carbamate, a thiocarbamate, a phosphorus derivative, or mixtures thereof.
 8. The lubricating oil of claim 1 wherein the surfactant comprises polyisobutylene succinimide polyamine (PIBSA-PAM).
 9. The lubricating oil of claim 1 wherein the swollen inverse micelles have a diameter of between 0.01 μm and 1 μm.
 10. The lubricating oil of claim 1 wherein the nonpolar lubricating oil base stock is present in an amount from 70 weight percent to 95 weight percent, and the one or more polar lubricating oil additives are present in an amount from 0.1 weight percent to 10 weight percent or greater, based on the total weight of the lubricating oil.
 11. The lubricating oil of claim 1 wherein the solubility of the polar lubricating oil additives in the nonpolar lubricating oil base stock is improved as compared to solubility achieved using a lubricating oil containing polar lubricating oil additives in a nonpolar lubricating oil base stock and not containing said swollen inverse micelles.
 12. The lubricating oil of claim 11 wherein the one or more polar lubricating oil additives comprise one or more inorganic friction modifiers, antioxidants, corrosion inhibitors, rust inhibitors, or mixtures thereof.
 13. The lubricating oil of claim 1 wherein surface performance in an engine is improved as compared to surface performance in an engine using a lubricating oil containing polar lubricating oil additives in a nonpolar lubricating oil base stock and not containing said swollen inverse micelles.
 14. The lubricating oil of claim 13 wherein surface performance comprises increasing thickness of a lubricating film at contacts requiring elastohydrodynamic lubrication (EHL) in said engine.
 15. The lubricating oil of claim 1 which is used in automotive, marine, aviation, and industrial engine and machine component applications.
 16. A method of improving solubility of polar lubricating oil additives in a nonpolar lubricating oil base stock, said method comprising providing a lubricating oil comprising a nonpolar lubricating oil base stock as a major component and one or more polar lubricating oil additives as a minor component; wherein said one or more polar lubricating oil additives comprise swollen inverse micelles dispersed in said nonpolar lubricating oil base stock; and wherein said swollen inverse micelles comprise (i) a liquid polar core containing a polar solvent and one or more polar lubricating oil additives having solubility in said polar solvent, and (ii) a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.
 17. The method of claim 16 wherein the nonpolar lubricating oil base stock comprises a Group I, Group II, Group III, Group IV or Group V base oil.
 18. The method of claim 16 wherein the polar solvent is selected from the group consisting of glycols, alcohols, esters, ethers, carboxylic acids, amines, organic compounds containing one or more polar functional groups, and mixtures thereof.
 19. The method of claim 16 wherein the one or more polar lubricating oil additives are selected from the group consisting of friction modifiers, antioxidants, corrosion inhibitors, rust inhibitors, metal deactivators, anti-wear agents and/or extreme pressure additives, dispersants, detergents, anti-seizure agents, wax modifiers, viscosity index improvers, viscosity modifiers, fluid-loss additives, seal compatibility agents, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, antifoam agents, and pour point depressants.
 20. The method of claim 16 wherein the one or more polar lubricating oil additives comprise one or more friction modifiers, antioxidants, corrosion inhibitors, rust inhibitors, or mixtures thereof.
 21. The method of claim 16 wherein the surfactant comprises a succinimide, a succinate ester, a succinate ester amide, a hydrocarbyl-substituted succinic acid derivative, a hydrocarbyl-substituted succinic anhydride derivative, an alkenylsuccinic derivative, or mixtures thereof.
 22. The method of claim 16 wherein the surfactant comprises a succinate ester, a phenate, a sulfonate, a sulfurized phenate, a salicylate, a naphthenate, a stearate, a carbamate, a thiocarbamate, a phosphorus derivative, or mixtures thereof.
 23. The method of claim 16 wherein the surfactant comprises polyisobutylene succinimide polyamine (PIBSA-PAM).
 24. The method of claim 16 wherein the swollen inverse micelles have a diameter of between 0.01 μm and 1 μm.
 25. The method of claim 16 wherein the nonpolar lubricating oil base stock is present in an amount from 70 weight percent to 95 weight percent, and the one or more polar lubricating oil additives are present in an amount from 0.1 weight percent to 10 weight percent or greater, based on the total weight of the lubricating oil.
 26. The method of claim 16 wherein the solubility of the polar lubricating oil additives in the nonpolar lubricating oil base stock is improved as compared to solubility achieved using a lubricating oil containing polar lubricating oil additives in a nonpolar lubricating oil base stock and not containing said swollen inverse micelles.
 27. The method of claim 26 wherein the one or more polar lubricating oil additives comprise one or more inorganic friction modifiers, antioxidants, corrosion inhibitors, rust inhibitors, or mixtures thereof.
 28. The method of claim 16 wherein surface performance in an engine is improved as compared to surface performance in an engine using a lubricating oil containing polar lubricating oil additives in a nonpolar lubricating oil base stock and not containing said swollen inverse micelles.
 29. The method of claim 28 wherein surface performance comprises increasing thickness of a lubricating film at contacts requiring elastohydrodynamic lubrication (EHL) in said engine.
 30. The method of claim 16 in which the lubricating oil is used in automotive, marine, aviation, and industrial engine and machine component applications.
 31. A method of improving surface performance of a lubricating oil in an engine lubricated with the lubricating oil, said method comprising using as the lubricating oil a formulated oil comprising a nonpolar lubricating oil base stock as a major component and one or more polar lubricating oil additives as a minor component; wherein said one or more polar lubricating oil additives comprise swollen inverse micelles dispersed in said nonpolar lubricating oil base stock; and wherein said swollen inverse micelles comprise (i) a liquid polar core containing a polar solvent and one or more polar lubricating oil additives having solubility in said polar solvent, and (ii) a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.
 32. The method of claim 31 wherein the nonpolar lubricating oil base stock comprises a Group I, Group II, Group III, Group IV or Group V base oil.
 33. The method of claim 31 wherein the polar solvent is selected from the group consisting of glycols, alcohols, esters, ethers, carboxylic acids, amines, organic compounds containing one or more polar functional groups, and mixtures thereof.
 34. The method of claim 31 wherein the one or more polar lubricating oil additives are selected from the group consisting of friction modifiers, antioxidants, corrosion inhibitors, rust inhibitors, metal deactivators, anti-wear agents and/or extreme pressure additives, dispersants, detergents, anti-seizure agents, wax modifiers, viscosity index improvers, viscosity modifiers, fluid-loss additives, seal compatibility agents, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, antifoam agents, and pour point depressants.
 35. The method of claim 31 wherein the one or more polar lubricating oil additives comprise one or more friction modifiers, antioxidants, corrosion inhibitors, rust inhibitors, or mixtures thereof.
 36. The method of claim 31 wherein the surfactant comprises a succinimide, a succinate ester, a succinate ester amide, a hydrocarbyl-substituted succinic acid derivative, a hydrocarbyl-substituted succinic anhydride derivative, an alkenylsuccinic derivative, or mixtures thereof.
 37. The method of claim 31 wherein the surfactant comprises a succinate ester, a phenate, a sulfonate, a sulfurized phenate, a salicylate, a naphthenate, a stearate, a carbamate, a thiocarbamate, a phosphorus derivative, or mixtures thereof.
 38. The method of claim 31 wherein the surfactant comprises polyisobutylene succinimide polyamine (PIB SA-PAM).
 39. The method of claim 31 wherein the swollen inverse micelles have a diameter of between 0.01 μm and 1 μm.
 40. The method of claim 31 wherein the nonpolar lubricating oil base stock is present in an amount from 70 weight percent to 95 weight percent, and the one or more polar lubricating oil additives are present in an amount from 0.1 weight percent to 10 weight percent or greater, based on the total weight of the lubricating oil.
 41. The method of claim 31 wherein the solubility of the polar lubricating oil additives in the nonpolar lubricating oil base stock is improved as compared to solubility achieved using a lubricating oil containing polar lubricating oil additives in a nonpolar lubricating oil base stock and not containing said swollen inverse micelles.
 42. The method of claim 41 wherein the one or more polar lubricating oil additives comprise one or more inorganic friction modifiers, antioxidants, corrosion inhibitors, rust inhibitors, or mixtures thereof.
 43. The method of claim 31 wherein surface performance in an engine is improved as compared to surface performance in an engine using a lubricating oil containing polar lubricating oil additives in a nonpolar lubricating oil base stock and not containing said swollen inverse micelles.
 44. The method of claim 43 wherein surface performance comprises increasing thickness of a lubricating film at contacts requiring elastohydrodynamic lubrication (EHL) in said engine.
 45. The method of claim 31 in which the lubricating oil is used in automotive, marine, aviation, and industrial engine and machine component applications.
 46. A swollen inverse micelle composition comprising (i) a liquid polar core containing a polar solvent and one or more polar lubricating oil additives having solubility in said polar solvent, and (ii) a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.
 47. A process for making a swollen inverse micelle composition, said process comprising: providing one or more polar lubricating oil additives, a polar solvent, and a surfactant; and mixing the one or more polar lubricating oil additives, the polar solvent, and the surfactant under conditions sufficient to form the swollen inverse micelle composition; wherein the swollen inverse micelle composition comprises (i) a liquid polar core containing the polar solvent and the one or more polar lubricating oil additives having solubility in said polar solvent, and (ii) a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.
 48. A lubricating oil comprising a nonpolar lubricating oil base stock as a major component and a polar lubricating oil additive as a minor component; wherein said polar lubricating oil additive comprises swollen inverse micelles dispersed in said nonpolar lubricating oil base stock; and wherein said swollen inverse micelles comprise (i) a liquid polar core containing a polar solvent and an antioxidant having solubility in said polar solvent, and (ii) a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.
 49. A lubricating oil comprising a nonpolar lubricating oil base stock as a major component and a mixture of polar lubricating oil additives as a minor component; wherein said mixture of polar lubricating oil additives comprises swollen inverse micelles dispersed in said nonpolar lubricating oil base stock; and wherein said mixture of swollen inverse micelles comprises: (a) a liquid polar core containing a polar solvent and an antioxidant having solubility in said polar solvent, and a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core; and (b) a liquid polar core containing a polar solvent and a friction modifier having solubility in said polar solvent, and a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core.
 50. A lubricating oil comprising a nonpolar lubricating oil base stock as a major component and a mixture of polar lubricating oil additives as a minor component; wherein said mixture of polar lubricating oil additives comprises (a) a first friction modifier comprising an organometallic molybdenum compound, and (b) a second friction modifier comprising swollen inverse micelles dispersed in said nonpolar lubricating oil base stock; wherein said swollen inverse micelles comprises a liquid polar core containing a polar solvent and an inorganic molybdate compound having solubility in said polar solvent, and a layer of liquid surfactant molecules enclosing said liquid polar core in which polar heads of the liquid surfactant molecules are oriented towards the liquid polar core; and wherein friction reduction and fuel efficiency are maintained or improved as compared to friction reduction and fuel efficiency achieved with a lubricating engine oil using singly the first friction modifier or the second friction modifier, as measured by one or more of ASTM D6079, SEQ VI-D and SEQ VI-E. 